With the SAT’s transition to a digital test, they’ve also integrated a digital calculator called Desmos. Students are now given access to a version of Desmos, a popular online graphing calculator, inside the Bluebook testing app for the entirety of the math section. While students can still bring their own scientific or graphing calculator, Desmos is faster and more powerful. Mastering Desmos will significantly improve students’ performance and consistency in the digital SAT math section. Let’s look at some Desmos tips below.
Stuck? Try graphing the function.
Any time a student doesn’t know what to do with a function, it’s a good idea to graph it on Desmos. Just as with strategies like using the answers and generating examples, graphing functions let students see the function’s visual image, which can make all the difference.
Once a function is graphed on Desmos, the calculator will put gray points on any mins, maxes, x-intercepts, and y-intercepts. When students hover over these points, they can see the exact coordinates, and when they click on them, the coordinates will be saved on the screen.
Using graphs to solve equations
Desmos is especially useful for finding intersections between lines. While some questions directly ask for the point where lines intersect—for instance, by asking for the solution to a system of equations—students can use Desmos to solve any single-variable equation.
To solve equations by graphing, students should type the left and right sides of the equation in separate lines.
To solve, say, 3x + 5 = 17, they would graph y = 3x + 5 as one equation, click or hit enter to move to the following line, and put y = 17 as a second equation. Desmos will put a gray point at the intersection between these two functions, and the x-value of that point will be the solution.
This is also useful for word problems that give students an x-value and ask for a y-value and vice versa. If a student is asked to evaluate y = 5x – 2 for x = 4, the answer will be the y-value of the intersection between those two lines.
How to practice outside of Bluebook
If students are practicing outside of the Bluebook, use the SAT’s version of Desmos here. The differences between this Desmos and the default web version are minimal, so students already used to using Desmos in class shouldn’t worry. The SAT version is intended as an offline calculator, so it disables some features. Otherwise, the SAT version of Desmos has a lot of the same features.
What if you can’t see your function?
If a student can’t see a function they’ve graphed or a key point is off-screen, there are several options. A student can click the plus or minus sign in the upper-right to zoom in or out. Students can click and drag to move the window, or click on the wrench and manually input a domain and range. If it looks like the function isn’t showing up at all and they’ve checked for typos, the student should make sure that a colored circle is showing immediately to the left of the equation—if an empty ring is showing, they can click on the ring to turn the designated graph back on.
Entering Calculations on Desmos
While most of the screen space on Desmos is dedicated to a graph, it also functions as a scientific calculator. Type in your calculation and the output will show on the bottom right of the box. Desmos also makes it easy to see if you have typed incorrectly as it is very easy to read fractions and exponents in its window. Students can quickly edit calculations so it makes it easy to enter multiple answer choices into Desmos.
Two common points of difficulty for students are fractions and exponents. To set up an expression with an exponent, students should click on the button showing a to the power of b, or type shift-6 on their keyboard. To exit an exponent (or a parenthesis, denominator, or radical), students click the right arrow on either the on-screen or physical keyboard. To get fractions, students can use the division sign. When done, students can immediately click the fraction symbol to the left of their computation to turn their answer from a decimal into a fraction.
Students have different preferences when it comes to calculators. Whether you use Desmos on the SAT or a hand-held calculator, students make the fewest mistakes when they write expressions by hand. So start by writing your work on paper and then type the entire expression into the calculator. That way, you make fewer mistakes while thinking through the most important aspects of the problems and avoid errors from doing multiple individual calculations.
Try out these Desmos tips and see how they work out for you!
