If sinA + sin2A = 1 then what is the value of cos2A + cos4A?
If sinA + sin2A = 1 then what is the value of cos2A + cos4A? Correct Answer 1
Given:
sinA + sin2A = 1
Formula used:
cos2A = 1 – sin2A
Calculation:
sinA + sin2A = 1 ----(i)
⇒ sinA = 1 – sin2A
⇒ sinA = cos2A ----(ii)
⇒ sin2A = cos4A ----(iii)
Now, we have to find cos2A + cos4A
From equation (ii) and (iii), we get
⇒ cos2A + cos4A = sinA + sin2A
⇒ cos2A + cos4A = 1
∴ cos2A + cos4A is 1.
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Feb 20, 2025