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Trig trick (Posted on 2002-11-07) Difficulty: 1 of 5
Prove that
    sin² x + cos² x = 1

See The Solution Submitted by Dulanjana    
Rating: 2.1818 (11 votes)

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By definition Comment 13 of 13 |
The unit circle is x² + y² = 1
cos(θ) = x coordinate of (1,0) under a rotation θ and
sin(θ) = y coordinate of (1,0) under a rotation θ by definition.

Substitute them in:
cos²(θ) + sin²(θ) = 1

  Posted by Jer on 2012-12-21 17:45:47
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