If sin4A = cos2A, find the value of A.

Solution:

Given,

$sin4A = cos2A$

or, $sin4A = sin(90 \textdegree -2A)$

or, $4A = 90 \degree - 2A$

or, $4A+2A = 90 \degree$

or, 6A = 90 \degree$

or, A = \frac{90 /degree}{6}$

$ \therefore A = 15 \degree$




To solve this question, we need to make the ratios in both LHS and RHS same. I.e. either sin or cos. 
For this, we know, cos(90°- A) = sinA

We will use the same identity and cancel the same term i.e. sin 
And the using the basic Mathematics, we can find the value of A which is 15°.

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