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Question
Prove the following trigonometric identities.
`cos theta/(1 + sin theta) = (1 - sin theta)/cos theta`
Solution
We know that `sin^2 theta + cos^2 theta = 1`
Multiplying both numerator and the denominator by `(1 - sin theta)`, we have
`cos theta/(1 + sin theta) = (cos theta(1 - sin theta))/((1 + sin theta)(1 - sin theta))`
`= (cos theta(1 - sin theta))/(1 - sin^2 theta)`
`= (cos theta (1 - sin theta))/cos^2 theta`
`= (1 - sin theta)/cos theta`
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= 12
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