Question

If sin a= 1/2 ,then the value of 3cos a-4cos cube a is:

Answer 1

Answer:

3cos a-4cos^3 a = 1

Step-by-step explanation:

sin a = 1/2

sin a = sin 45

so ,  a= 45

then ,

3cos a - 4cos cube a

3 cos 45 - 4 cos^3  45

3 × 1/2 - 4 × (1/2)^3

3/2 - 4 × 1/8

3/2 - 1/2 = 2/2 = 1

Answer 2

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As it would be a right angled triangle,

We know that,

$\implies$ Sin(A) = 1/2

$\implies$ Cos(A) = √3/2

Now,

$\implies$ Cos³(A)

$\implies$ 3Cos(A) - 4Cos³(A)

$\implies$ 3√3/2 - 43√3/8

$\implies$ 3√3/2 - 3√3/2

$\implies$ 0

Hence Proved!!

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