हिंदी

Prove that sin θ (1 – tan θ) – cos θ (1 – cot θ) = cosec θ – sec θ.

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प्रश्न

Prove that sin θ (1 – tan θ) – cos θ (1 – cot θ) = cosec θ – sec θ.

प्रमेय
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उत्तर

L.H.S. = sin θ (1 – tan θ) – cos θ (1 – cot θ)

= `sin θ (1 - (sin θ)/(cos θ)) - cos θ (1 - (cos θ)/(sin θ))`

= `sin θ - (sin^2θ)/(cosθ) - cos θ + (cos^2θ)/(sinθ)`

= `sin θ + (cos^2θ)/(sinθ) - (sin^2θ)/(cosθ) - cos θ`

= `(sin^2θ + cos^2θ)/(sinθ) - ((sin^2θ + cos^2θ)/(cosθ))`

= `1/(sinθ) - 1/(cosθ)`   ...[∵ sin2θ + cos2θ = 1]

= cosec θ – sec θ

= R.H.S.

∴ sin θ (1 – tan θ) – cos θ (1 – cot θ) = cosec θ – sec θ

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