Q22 of 153 Page 7

If cos A + cos2 A = 1, then sin2 A + sin4 A

Given: cos A + cos2 A = 1

⇒ cos A = 1 – cos2 A = sin2 A [∵ sin2 A + cos2 A = 1]……(i)


Squaring both sides, we get


⇒ cos2 A = (sin2 A)2 = sin4 A ……(ii)


To find: sin2 A + sin4 A


Consider sin2 A + sin4 A = cos A + cos2 A [From (i) and (ii)]


= 1

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