Mastering the SAT Desmos Calculator
On the Digital SAT, the embedded calculator isn’t just for checking arithmetic—it’s a problem-solving superpower. Here are Wizdomi’s top tricks to save time and boost accuracy.
1. Don’t Solve, Just Graph
Faced with a “system of linear equations” problem? Don’t use substitution or elimination algebraically.
The Trick: Type both equations exactly as they appear into two separate command lines. The solution is simply the point where the two lines cross. Hover over the intersection point to see the coordinates.
Works for quadratic systems (parabolas vs lines) too!
2. The “Table Data” Hack
If the SAT gives you a table of X and Y values and asks for the equation of the line (or “line of best fit”).
The Trick:
- Click the + button and add a Table.
- Enter the points from the SAT problem into the table.
- In a new command line, type this magic formula:
y1 ~ mx1 + b
Desmos will instantly calculate the slope (m) and y-intercept (b) for you.
3. Define Variables First
If a problem says “If $x = 5$ and $y = 3$, what is the value of $\frac{4x^2 – 2y}{x+y}$?”
The Trick: Don’t plug numbers in manually.
Line 1: Type x = 5
Line 2: Type y = 3
Line 3: Type the complex expression (4x^2 – 2y) / (x+y)
The calculator will spit out the answer instantly.
4. The Trigonometry Trap
The most common mistake on SAT Trig problems occurs before you even type a number.
The Rule: Are you working with $\sin$, $\cos$, or $\tan$? Check the problem. If the angles are in degrees (e.g., $45^\circ$), you MUST open the Wrench Settings icon (top right) and ensure “Degrees” is selected. If the angles look like $\frac{\pi}{2}$, select “Radians.”