Three Points Generate Every Exact Value

You'll learnto generate every special-angle value from three first-quadrant angles.

Three first-quadrant angles carry every exact value on the exam. Every other special angle is one of those three, folded into another quadrant by its reference angle, with the signs read straight off the coordinates. Watch the folding happen, and watch the classic coordinate swap get struck out.

8 STEPS · 6 QUICK CHECKS · SPECIAL ANGLES · REFERENCE ANGLES · SIGNS · v2

fold, then sign

Before you start

What you're looking at

The angle π/4 built first from a triangle, with degree and radian labels shown together.

The question

Which coordinate is the cosine, and which is the sine?

Watch for

Cosine as the horizontal coordinate and sine as the vertical — the source of the classic coordinate swap.

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