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If y=sin θ (theta), what is cos θ in terms of y?

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lameduck27 | (Level 1) eNoter

Posted September 30, 2013 at 4:14 PM via web

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If y=sin θ (theta), what is cos θ in terms of y?

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ishpiro | Teacher | (Level 2) Associate Educator

Posted September 30, 2013 at 4:23 PM (Answer #1)

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Use Pythagorean identity to answer this question:

`sin^2(theta) + cos^2(theta) = 1` 

Plug in `sin(theta) = y:`

`y^2 + cos^2(theta) = 1`

` cos^2(theta) = 1-y^2`

`cos(theta) = +-sqrt(1 - y^2)`

` `

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