Is Desmos allowed on the AP Precalculus exam?

Yes, on the calculator parts only. Bluebook has Desmos built in for Section I Part B and Section II Part A. It isn't available on Section I Part A or Section II Part B.

Can I use my own calculator on the AP Precalculus exam?

Yes, if it's an approved handheld graphing calculator. Check the College Board's current list before exam day.

How do I do a regression in Desmos?

Enter the data in a table, which Desmos labels x1 and y1, then type the model with a tilde in place of the equals sign, such as y1 ~ a b^x1 for an exponential model. Desmos lists the fitted parameters below that line.

How many decimal places do I need on the AP Precalculus exam?

On free response, decimal answers should be correct to three places after the decimal point unless the question says otherwise. Round only at the end.

How to use Desmos on the AP Precalculus exam

Updated November 10, 2026

The AP Precalculus exam is given in the Bluebook app, and Desmos is built into Bluebook on the calculator parts. An approved handheld graphing calculator is also allowed if you prefer one.

Calculator questions in precalculus keep asking for the same few things: solve an equation by finding an intersection, fit a regression to a table, find a maximum, minimum, or zero, evaluate a model, and check an answer. This guide shows each one in Desmos with a worked example. Then it covers the bigger half of the exam, where there's no calculator at all.

Where Desmos is available

Section I, Part B: 13 multiple-choice questions in 40 minutes, calculator required, 18.75% of your score.
Section II, Part A: 2 free-response questions in 35 minutes, calculator required, 18.75% of your score. These are Function Concepts and Modeling a Non-Periodic Context.
Section I, Part A and Section II, Part B: no calculator. These parts hold 29 multiple-choice questions and 2 free-response questions, and they make up 62.5% of your score.

So Desmos covers a bit over a third of your score. The AP Precalculus exam format guide has the full breakdown.

1. Solve an equation by finding the intersection

When an equation mixes function types, like a sine and a line or an exponential and a polynomial, there's often no way to solve it by hand. Graph each side as its own $y =$ line and click the points where the graphs cross. The $x$ -coordinate of each crossing is a solution.

A sine curve and a line

Find all solutions of

4\sin(x) = x + 1

for

x

between

0

and

2\pi

, inclusive.

1Type $y = 4\sin(x)$ on one line and $y = x + 1$ on the next.
2Click either curve. Desmos marks the crossings as gray points.
3Click each gray point to see its coordinates: $(0.342, 1.342)$ and $(2.210, 3.210)$ .
4Past $x = 2.210$ the line stays above the sine curve all the way to $2\pi \approx 6.283$ , so there are no more solutions in the interval.

y = 4\sin(x)

y = x + 1

Answer: $x \approx 0.342$ and $x \approx 2.210$

Zoom out before you count

How many real solutions does the equation

2^x = x^2 + 1

have?

Graph $y = 2^x$ and $y = x^2 + 1$ . In the default view you see two crossings, at $(0, 1)$ and $(1, 2)$ , and the parabola looks like it pulls away for good.

Zoom out, or make the $y$ -axis taller. An exponential with base greater than $1$ eventually grows faster than any polynomial, so it has to catch up. It does, at about $(4.257, 19.126)$ . To the left of $x = 0$ , $2^x$ stays below $1$ while $x^2 + 1$ is at least $1$ , so there are no crossings there.

y = 2^x

y = x^2 + 1

The third crossing sits above the default view.

Answer: $3$ solutions

2. Click the gray points: maximums, minimums, and zeros

Click any graph and Desmos marks its $x$ -intercepts and its turning points. That replaces a lot of algebra. Two habits matter: look at the endpoints of the interval the question gives you, and read the right coordinate. The $x$ -coordinate tells you where, and the $y$ -coordinate tells you how much.

Absolute extremes on an interval

A small company's monthly profit, in thousands of dollars, is modeled by

P(x) = -0.5x^3 + 6x^2 - 15x + 4

, where

x

is the number of months since it opened, for

x

from

0

10

. Find the greatest and least values of

P

on this interval.

1Type $P(x) = -0.5x^3 + 6x^2 - 15x + 4 \{0 \le x \le 10\}$ . The braces limit the graph to the interval.
2Click the curve. Desmos marks a low point at $(1.551, -6.697)$ and a high point at $(6.449, 22.697)$ .
3Check the endpoints too. Type $P(0)$ and $P(10)$ : Desmos shows $4$ and $-46$ .
4Compare all four values. The greatest is $22.697$ at the turning point. The least is $-46$ at the endpoint $x = 10$ , well below the turning point's $-6.697$ .

P(x)

Answer: Greatest: about $22.697$ thousand dollars at $x \approx 6.449$ . Least: $-46$ thousand dollars at $x = 10$ .

When the profit is negative

Using the same model

P

for

x

from

0

10

, during which months is the company losing money?

Losing money means $P(x) < 0$ , so you need the zeros. Click the curve and Desmos marks three $x$ -intercepts: $x \approx 0.302$ , $x \approx 3.066$ , and $x \approx 8.632$ .

Between the zeros the sign can't change, so read it off the graph. The curve is below the axis from $0.302$ to $3.066$ and again from $8.632$ to the end of the interval.

Answer: $0.302 < x < 3.066$ and $8.632 < x \le 10$

3. Fit a regression to a table

Precalculus asks you to build models from data. In Desmos, add a table with the plus button, type the data into $x_1$ and $y_1$ , then type a regression with a tilde ( $\sim$ ) on a new line. Desmos finds the parameters and lists them under the line.

Linear: $y_1 \sim mx_1 + b$
Quadratic: $y_1 \sim ax_1^2 + bx_1 + c$
Cubic: $y_1 \sim ax_1^3 + bx_1^2 + cx_1 + d$
Exponential: $y_1 \sim ab^{x_1}$
Logarithmic: $y_1 \sim a + b\ln(x_1)$
Sinusoidal: $y_1 \sim a\sin(b(x_1 - c)) + d$

A medication leaving the body

The amount of a medication in a patient's bloodstream was measured every hour. At 0, 1, 2, 3, 4, and 5 hours after the dose, the amounts were 200, 161, 133, 107, 88, and 71 milligrams. Use an exponential regression to model the amount, then use the model to estimate the amount after 8 hours.

1Add a table. Type the hours into the $x_1$ column and the milligrams into the $y_1$ column.
2On a new line, type $y_1 \sim ab^{x_1}$ .
3Desmos reports $a \approx 199.456$ and $b \approx 0.81376$ , with $R^2 \approx 0.9997$ . The model is $M(t) = 199.456(0.81376)^t$ .
4On a new line, type $ab^8$ . Desmos uses its stored values of $a$ and $b$ and shows about $38.354$ .

y_1 \sim ab^{x_1}

If you round $b$ to $0.814$ first and compute $199.456(0.814)^8$ , you get about $38.445$ , which is off in the first decimal place. Let Desmos keep the full values.

Answer: About $38.354$ milligrams

Choosing which model to fit, and reading residuals, are covered in the AP Precalculus regression guide.

4. Evaluate a model with function notation

Give the model a name, like $P(t) =$ instead of $y =$ . Then you can type $P(10)$ or a whole average rate of change on one line, and Desmos does the arithmetic with no rounding in between.

A growing town

The population of a town, in thousands of people, is modeled by

P(t) = 18.4(1.027)^t

, where

t

is the number of years since 2015. (a) Find the average rate of change of

P

from

t = 2

t = 10

. (b) Find the value of

t

when the population reaches 30 thousand.

1Type $P(t) = 18.4(1.027)^t$ . Any letter can be the input in a named function.
2For (a), type $\frac{P(10) - P(2)}{10 - 2}$ . Desmos shows about $0.57627$ .
3For (b), graph $y = P(x)$ and $y = 30$ , then click the crossing. It's at $x \approx 18.349$ .

Give units with each answer. The average rate of change is in thousands of people per year, and the answer to (b) is a number of years after 2015, so partway through 2033.

Answer: (a) About $0.576$ thousand people per year. (b) $t \approx 18.349$

5. Check an answer you found by hand

Even on a calculator part, some questions are faster by hand. Desmos is still useful afterward: plug your answer back in, or graph both sides and see if the crossing matches. This catches extraneous solutions from logs and square roots.

A log equation with a trap

Solve

\log_3(x) + \log_3(x - 8) = 2

By hand: combine the logs to get $\log_3(x(x - 8)) = 2$ , so $x(x - 8) = 9$ . That gives $x^2 - 8x - 9 = 0$ , or $(x - 9)(x + 1) = 0$ , so $x = 9$ or $x = -1$ .

1Check in Desmos. Type $\log_3(9) + \log_3(9 - 8)$ . It shows $2$ , so $x = 9$ works.
2Type $\log_3(-1)$ . Desmos shows undefined, because a log's input has to be positive. Reject $x = -1$ .
3For a picture, graph $y = \log_3(x) + \log_3(x - 8)$ and $y = 2$ . There's one crossing, at $(9, 2)$ .

Answer: $x = 9$

Desmos reads $\log$ as base $10$ and $\ln$ as base $e$ . For any other base, type it with a subscript, like $\log_3$ above. More on solving these exactly is in the exponential and log equations guide.

When not to reach for Desmos

Section I Part A and Section II Part B have no calculator, and together they're 62.5% of your score. That's where most of your study time should go. These are the skills you need by hand:

Rational functions: zeros, vertical asymptotes, holes, and end behavior from the factored form. See the rational functions guide.
Exponent and log rules: rewriting expressions and solving equations exactly.
Unit circle values: sine, cosine, and tangent at the standard angles, plus inverse trig values.
Sinusoidal models: building a function from a maximum, a minimum, and a period, which is what FRQ 3 asks. See the sinusoidal models guide.
Polar graphs: reading where $r$ is increasing or decreasing, and when the point is moving toward or away from the origin. See the polar functions guide.

Even on the calculator parts, not every question needs Desmos. If you can see the answer from a table or a quick rewrite, typing a graph can take longer. Use Desmos when the equation can't be solved by hand, when there's data to fit, or when you want to check your work.

On free response, the people scoring your answers can't see your screen. Write the equation you solved or the model you used before the number. Showing that setup is how graders can award points, and it's good practice. The free-response guide covers each question type.

Keep going

Practice on exam-style questions

Intersect Prep has 349 multiple-choice questions across all 3 exam units, with a full solution for each one. Create a free account to try a full lesson with the calculator. One payment of $29 unlocks the course for 3 months, or $39 for 6 months.

Try a free lesson See the course

Questions

Is Desmos allowed on the AP Precalculus exam?: Yes, on the calculator parts only. Bluebook has Desmos built in for Section I Part B and Section II Part A. It isn't available on Section I Part A or Section II Part B.
Can I use my own calculator on the AP Precalculus exam?: Yes, if it's an approved handheld graphing calculator. Check the College Board's current list before exam day.
How do I do a regression in Desmos?: Enter the data in a table, which Desmos labels x1 and y1, then type the model with a tilde in place of the equals sign, such as y1 ~ a b^x1 for an exponential model. Desmos lists the fitted parameters below that line.
How many decimal places do I need on the AP Precalculus exam?: On free response, decimal answers should be correct to three places after the decimal point unless the question says otherwise. Round only at the end.