ACT Preparation / Unit 14 ACT 1325 short lesson, about 20 seconds
The Unit Circle
Captions available
The idea
On the unit circle, of radius 1 centered at the origin, an angle θ from the positive x-axis meets the circle at the point (cos θ, sin θ).
In practice
At 90°, the point is (0, 1), so cos 90° = 0 and sin 90° = 1.
Where people slip
Signs follow the quadrant: in the second quadrant, cosine is negative and sine positive.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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