Question

If sin α = `1/2`, then find the value of (3 cos α – 4 cos³ α).

Answer 1

Given that,

sin α = `1/2`

So, sin α = sin 30° = `1/2`

`\implies` α = 30°

Now, (3 cos α – 4 cos³ α)

= (3 cos 30° – 4 cos³ 30°)

= `(3 xx sqrt(3)/2 - 4 xx (sqrt(3)/2)^3)`

= `(3sqrt(3))/2 - (3sqrt(3))/2`

= 0