Foundation
Mathematics Foundation
Introduction to Trigonometry
Question

If sin A + sin2A = 1 then cos2A + cos4A = ?

3

1

12

2

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Solution

Since,  sin A + sin2A = 1 therefore,  sin A = 1 - sin2A  =cos2A

 Hence, cos2A + cos4A = sin A + sin2A = 1