Desmos inside the SAT: the graphing skill your school probably didn't cover
The built-in calculator is a full graphing engine. Students who treat it as a first resort finish math modules with minutes to spare.
By the Brilliant Tutors team · 5 min read · Stage 2 of 5: Foundations
Most high schools teach students to solve math problems by hand. That is good for learning. It is bad for the digital SAT. The test comes with a full-featured graphing calculator built in, and the students who use it aggressively gain points faster than the students who treat it as a last resort.
What Desmos actually is
The Desmos tool inside Bluebook is not the four-function calculator your teacher let you use in ninth grade. It is a full graphing engine. You can type equations, plot them, find intersections, drag points, and add sliders that let you see what changes when a coefficient moves. It costs nothing to use and it is embedded in every math question.
Four patterns where Desmos beats hand work
Reach for the calculator when
- A parabola, circle, or any curve appears in the question. Plot it. Read the answer off the graph. Stop doing algebra in your head.
- You have a system of two equations. Type both equations. The intersection point is your answer. You do not need to remember substitution or elimination.
- The problem involves an inequality. Plot the inequality. Shaded regions tell you which answer choices are valid at a glance.
- You are unsure what the question is asking. Graph what you have and look. Sometimes the shape of the answer is obvious once you see it.
The sliders trick
Here is the one Desmos feature that even strong math students miss. Type an equation with a letter for a coefficient, like y = ax² + 3. Desmos will ask if you want to add a slider for a. Say yes. Drag the slider. You can watch in real time how the parabola changes as a moves. Questions about "what happens if we change this coefficient" stop being algebra problems and become one-second visual answers.
When not to use it
For a pure arithmetic calculation, a simple system of one-variable equations, or any problem you can see the answer to in ten seconds, skip the calculator. The time cost of typing the equation in is the only real penalty, and it adds up. The rule: if Desmos would take longer to set up than the problem would take to solve by hand, do it by hand.
One student we worked with had been getting the geometry questions about circles wrong for a month. She knew the formulas. She just kept mis-applying them under time pressure. Two afternoons of Desmos practice later she stopped using the formulas entirely and started plotting the circles. Her circle-question accuracy went from 40% to 90% in a week.
Try this week
Take any practice math question involving a curve or a system. Solve it the normal way, then solve it again with Desmos. Note which one was faster. Repeat for five questions. You will build a sense of when to reach for the tool.
Ready to put this into practice? Start your free diagnostic and get a study plan built around what you just read.
More from this stage of the journey.
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Coming soon in batch 2.
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Put it into practice.
Reading about prep is good. Doing it is better.