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