Mistake Master
Mistake Master · AP Precalculus · Unit 3 · Step-Through Animation
An Identity Is a Promise for Every Input
You'll learnto tell an identity (true for every input) from an equation (true for only some).
An identity is a claim that two expressions agree at every angle, which is why no pile of examples proves one and a single angle can destroy one. Watch an invented rule die on one input, then watch the real ones come off the unit circle. Twelve short steps; press Next for each one.
no pile of examples proves it · one input can kill it
Before you start
What you're looking at
A unit circle carrying two angles and the ray for their sum.
The question
Does a claimed rule hold for every legal input, or only for a few?