Question

trigonometric equations​

Answer 1

If sinθ=sinα, then θ=nπ+(−1)nα. Thus, if n is odd, θ=(2m+1)π−α and if n is even, θ=2mπ+α.

If cosθ=cosα, then θ=2nπ±α.

If tanθ=tanα, then θ=nπ+α.

Answer 2

Given , sinx = 3/5

$cos2x = 1 - 2 {sin}^{2} x\\ \\ = > cos2x = 1 - 2 \times \frac{ {3}^{2} }{ {5}^{2} } \\ \\ = > cos2x = 1 - 2 \times \frac{9}{25} \\ \\ = > cos2x = 1 - \frac{18}{25} \\ \\ = > cos2x = \frac{25 - 18}{25} \\ \\ = > cos2x = \frac{7}{25}$

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