1.

If sinx = √5/3 and 0 < x < π/2, find the values of cos 2x

Answer»

Given: sinx = \(\frac{\sqrt{5}}{3}\)

To find: cos2x

We know that,

cos2x = 1 – 2sin2x

Putting the value, we get

cos2x = 1 - 2\((\frac{\sqrt{5}}{3})^{2}\)

cos2x = 1 - 2 x \(\frac{5}{9}\)

cos2x = 1 - \(\frac{10}{9}\)

cos2x = \(\frac{9\,-\,10}{9}\)

∴ cos2x = -\(\frac{1}{9}\)



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