ACT Desmos quickstart

On the online ACT, Desmos is built into the Math section. If you are taking the paper test, practice with your permitted handheld calculator; a separate phone or computer is not an allowed calculator. See ACT's calculator policy.

For practice, open desmos.com/practice, select Choose Assessment → ACT (ACT and PreACT), then Graphing Calculator ACT Version → Start Practice. Use this version for the examples below.

Get comfortable with the controls

Type in the expression list on the left. Graphs appear on the right. The keypad opens at the bottom; the plus button adds items such as tables. Use the wrench to open Graph Settings, including angle units and axis bounds. If a point is outside the visible graph, zoom out or change the bounds.

The ACT configuration defaults to degrees. Confirm the units before trig work; a radian question needs radians. The ordinary Desmos calculator and the SAT version have different settings.

These examples and exercises are original Sharp practice. Use the sheet while studying, not as material to bring into the testing room. The following pages show both what to enter and how to interpret the result.

One unknown: graph each side

To solve 3(x − 2) = x + 8, enter one side on each line:

y=3(x-2)

y=x+8

Select a line, then select the gray point where the lines cross. The intersection is (7, 15), so x = 7. The y-value is what both expressions equal; it is not the solution requested.

Check: 3(7 − 2) = 15 and 7 + 8 = 15. By hand, 3x − 6 = x + 8 gives 2x = 14. For short equations like this, algebra is also a quick option.

Two unknowns: keep the ordered pair

For the system below, enter each equation on its own line:

y=2x+1

y=-x+10

The intersection is (3, 7). If the question asks for y, answer 7. If it asks for x + y, answer 10. Check both equations: 2(3) + 1 = 7 and −3 + 10 = 7.

An empty window does not prove there is no solution. Check the input and zoom before drawing a conclusion. When a line meets a curve, look for every intersection and apply any domain restrictions in the question.

Zeros and maximum values answer different questions

y=-x^2+8x+9

Select the curve, then its gray points. The x-intercepts are (−1, 0) and (9, 0), so −x² + 8x + 9 = 0 has solutions −1 and 9. The vertex is (4, 25). The maximum value is 25; it occurs at x = 4. Set the upper y-bound above 25 if the vertex is outside your window.

Check: −x² + 8x + 9 = −(x − 4)² + 25. The squared term cannot be negative, so subtracting it gives a value no greater than 25. Substituting −1 or 9 gives 0.

To solve −x² + 8x + 9 = 16 instead, add y=16 and use its intersections with the curve. The x-intercepts answer the equation with 0 on the other side.

Define a function once, then give it inputs

f(x)=x^2-3x+4

f(-2)

The result is 14: (−2)² − 3(−2) + 4 = 4 + 6 + 4. Keep the negative input in parentheses when you check by hand.

To compare several inputs, choose Add Item (+) → Table. Put −2, 0 and 3 in the x₁ column. Replace the second column heading with f(x_1): type f(x_1, press the right arrow to leave the subscript, then type the closing parenthesis. Desmos fills the outputs:

A table checks the inputs you enter. Matching a few rows does not prove two expressions are equal for every x. If a question supplies a table, test each given row before choosing a matching rule.

The ACT calculator starts in degrees, according to Desmos's ACT configuration sheet. Open Graph Settings and check Degrees or Radians to match the question.

A side from an angle in degrees

In a right triangle, an angle measures 35° and its adjacent leg is 12 cm. Find the opposite leg h. Tangent uses opposite ÷ adjacent, so tan 35° = h/12 and h = 12 tan 35°.

In degree mode, enter:

12tan(35)

The result is about 8.40249, so h is 8.4 cm to the nearest tenth. If the answer choices are expressions, 12 tan 35° already answers the question; you may not need a decimal.

A question in radians

To evaluate sin(π/6), switch to radian mode and enter sin(pi/6). The result is 0.5, because π/6 radians is 30°. The same input in degree mode interprets π/6 as about 0.524 degrees.

Before the next trig question, check its units again. For a degree check, sin(30) should give 0.5. A familiar-looking decimal is not enough to establish that the mode is right.

Primary references, checked November 5, 2026: ACT calculator policy; Desmos ACT settings, SY2026–2027; ACT calculator tutorials. Practice with the ACT test calculator before trying the exercises.

Try these original tasks in the ACT practice calculator. Record the input, the result and a check by substitution or algebra. These are skill exercises, not a scored ACT section.

Keep your work visible. For the trig questions, write the angle mode before entering the expression.