How to solve
On the unit circle, cosine is the x-coordinate and sine is the y-coordinate of the point at angle θ from the positive x-axis. Memorizing the standard first-quadrant landmarks (and their reflections) gives exact values without a calculator.
Steps
- Recall the standard angles: 0, π/6, π/4, π/3, π/2 (and their quadrant reflections).
- Read cos θ as the x-coordinate and sin θ as the y-coordinate.
- Use exact radical forms for the familiar values.
Example
Find sin(π/3).
- π/3 is a standard first-quadrant angle with y-coordinate √3/2.
- So sin(π/3) = √3/2.
Answer: sqrt(3)/2
How to type answers
- Use sqrt(n) for radicals, e.g. sqrt(2)/2 or sqrt(3)/2
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