Question

if sin3A=1 find the cos 2A​

Answer 1

Answer:

$\cos(2a) = \frac{1}{2}$

Step-by-step explanation:

$\sin(3a) = 1$

$\sin(90) = 1$

Therefore,

$3a = 90$

$a = \frac{90}{3} = 30$

$\cos(2a) = \cos(2 \times 30) = \cos(60) = \frac{1}{2}$

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Answer 2

Answer:

1/2

sin3A = 1, then sin3A =sin90°,since sin 90°=1, 3A=90°thenA=30°

now,cos2A=cos2*30°=cos60°

and value of cos 60° is 1/2