Question Details

3cos3θ2cosθsinθ3sin3θ is equal to:

Options

A

tan2θ

B

tanθ

C

cot2θ

D

cotθ

Show Answer

Correct Answer :

Option D

cotθ

Solution :

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The correct answer is cotθ.

To simplify the given trigonometric expression:

3cos3θ2cosθsinθ3sin3θ

Step 1: Factor out common terms from the numerator and denominator.
In the numerator, factor out cosθ:
3cos3θ2cosθ=cosθ(3cos2θ2)

In the denominator, factor out sinθ:
sinθ3sin3θ=sinθ(13sin2θ)

So, the expression becomes:

cosθ(3cos2θ2)sinθ(13sin2θ)

Step 2: Use the trigonometric identity cos2θ=1sin2θ to rewrite the numerator term.
Substitute cos2θ=1sin2θ into 3cos2θ2:

3(1sin2θ)2=33sin2θ2=13sin2θ

Step 3: Simplify the expression.
Substitute this back into the numerator:

cosθ(13sin2θ)sinθ(13sin2θ)

Cancel out the common term (13sin2θ) from both the numerator and denominator:

cosθsinθ=cotθ

Thus, the expression simplifies to cotθ.

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