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Maharashtra State BoardSSC (English Medium) 10th Standard

Prove that: cos2θ (1 + tan2θ)

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Question

Prove that:

cos2θ (1 + tan2θ)

Sum
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Solution

L.H.S. = cos2θ (1 + tan2θ)

= cos2θ × sec2θ          ...[∵ 1 + tan2 θ = sec2 θ]

= \[\cos^{2}\theta\times\frac{1}{\cos^{2}\theta}\]

= 1

= R.H.S.

∴ cos2θ (1 + tan2θ) = 1

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Chapter 6: Trigonometry - Practice Set 6.1 [Page 131]

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\[\frac{1}{1 - \sin\theta} + \frac{1}{1 + \sin\theta} = 2 \sec^2 \theta\]

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Proof: L.H.S. = (sec θ – cos θ) (cot θ + tan θ)

= `(1/square - cos θ) (square/square + square/square)` ......`[∵ sec θ = 1/square, cot θ = square/square and tan θ = square/square]`

= `((1 - square)/square) ((square + square)/(square  square))`

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 = `square/(square  square)`

= tan θ.sec θ

= R.H.S.

∴ L.H.S. = R.H.S.

∴ (sec θ – cos θ) (cot θ + tan θ) = tan θ.sec θ


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