1.

If sin x + sin2x = 1, then value of cos2x + cos4 x is1). 12). 23). 1.54). None of these

Answer»

sin x + sin2 x = 1----(1)

cos2 x + cos2 x = ?----(2)

From equation (1)

sin x + sin2 x = 1 (sin2x + cos2x = 1)

sin x + 1 – cos2 x = 1

sin x = cos2 x

sin2 x = cos4 x

substituting VALUE of cos2 x and cos4 x in (2)

cos2 x + cos4 x = sin x + sin2 x = 1


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