Pythagorean identity

What this lesson shows

From our triangle, sine of theta is 0.6 and cosine is 0.8. Square them both… and watch what they add up to.

Try it yourself

Real questions from this lesson's worksheets — answers below each one.

1. Convert 5π/6 radians to degrees
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   150°
2. sin θ = 3/5. Find cos θ (acute angle)
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   4/5
3. Complete the identity: sin²θ + ___ = 1
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   cos²θ
4. sin θ = 3/5. Evaluate sin²θ + cos²θ
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   1