Question Details

Find the value of cosecθ(1cosθ)(cosecθ+cotθ).

Options

A

2

B

-1

C

1

D

0

Show Answer

Correct Answer :

Option C

1

Solution :

The correct answer is 1.

To evaluate the trigonometric expression:

cosecθ(1cosθ)(cosecθ+cotθ)

We can express all trigonometric functions in terms of sinθ and cosθ using the basic identities:
cosecθ=1sinθ
cotθ=cosθsinθ

Substituting these into the given expression, we get:

=1sinθ(1cosθ)1sinθ+cosθsinθ

Simplify the term in the second parenthesis by finding a common denominator:

=1sinθ(1cosθ)1+cosθsinθ

Combine the numerators and denominators:

=(1cosθ)(1+cosθ)sin2θ

Using the algebraic difference of squares formula, (ab)(a+b)=a2b2:

=1cos2θsin2θ

By the fundamental Pythagorean trigonometric identity, sin2θ+cos2θ=1, we know that 1cos2θ=sin2θ. Substituting this into the numerator:

=sin2θsin2θ=1

Thus, the simplified value of the expression is 1.

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