Question

step by step explanation plsssss​

Answer 1

Cos(3A) = 4cos³(A) - 3cos(A)

at A = 30°

cos(3*30) = 4cos³(30) - 3cos(30)

cos(90) = 4cos³(30) - 3cos(30)

0 = 4(√3/2)³ - 3(√3/2)

0 = 4(3√3/8) - 3√3/2

0 = 3√3/2 - 3√3/2

0 = 0

Hence, it is verified that the given equation holds true for A = 30°.

Answer 2

Step-by-step explanation:

In, $\rm {cos3A = 4cos^3A - 3cosA}$

Substituting, A = 30°

⇒ cos3(30) = 4 cos³(30) - 3cos30

⇒ cos90 = 4 ( 3√3/8) - 3√3 /2

0 = 0

Hence verified

Hope it helps

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