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Mathematics

Assertion (A): (1 − cosec2 θ)(1 − sec2 θ) = 1

Reason (R): 1 + tan2 θ = sec2 θ and 1 + cot2 θ = cosec2 θ

  1. A is true, R is false

  2. A is false, R is true

  3. Both A and R are true

  4. Both A and R are false

Trigonometric Identities

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Answer

Solving L.H.S,

(1 − cosec2 θ)(1 − sec2 θ)

= (− cot2 θ)(− tan2 θ)

= 1tan2θ\dfrac{1}{\tan^2 \theta} (tan2 θ)

= 1

L.H.S = R.H.S

Therefore, assertion (A) is true.

1 + tan2 θ = sec2 θ and 1 + cot2 θ = cosec2 θ

These are standard trigonometric identities derived from the unit circle and the Pythagorean theorem.

Therefore, reason (R) is true.

Both A and R are true.

Hence, option 3 is the correct option.

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