Brainlag Plusy = −f(x) and y = f(−x), the graphs of sin x, cos x and tan x, exact values, and solving sin x = k and cos x = k.
Two reflections
- y = −f(x) changes the sign of every y value: a reflection in the x-axis. (3, 5) goes to (3, −5).
- y = f(−x) changes the sign of every x value: a reflection in the y-axis. (3, 5) goes to (−3, 5).
For f(x) = x² + 2x − 3: −f(x) = −x² − 2x + 3, and f(−x) = (−x)² + 2(−x) − 3 = x² − 2x − 3. In f(−x), even powers of x keep their sign and odd powers change sign.
The rest of this lesson and its 7 practice questions are in Plus.
Screen 1 of 4, free to read.
- 7 exam-style questions, marked as you go, each with a worked solution
- The Unit Circle beside every question
- Anything you get wrong is saved to your flashcards