Q12 of 44 Page 80

Find the value of 4cos330° – 3 cos30°.

For θ = 30°,


4cos330° – 3 cos30° = 4cos3θ– 3cosθ


We know that,


cos3θ = 4cos3θ– 3cosθ


∴ 4cos330° – 3 cos30°


= cos(3 × 30° )


= cos90°


= 0


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