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Maharashtra State BoardSSC (English Medium) 10th Standard

Prove the following. secθ (1 – sinθ) (secθ + tanθ) = 1

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Question

Prove the following.

secθ (1 – sinθ) (secθ + tanθ) = 1

Sum
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Solution

secθ (1 – sinθ)(secθ + tanθ) = 1

LHS = secθ (1 – sinθ)(secθ + tanθ)

LHS = (secθ – secθ sinθ)(secθ + tanθ)

`"LHS" = (secθ  –  1/cosθ × sinθ)(secθ + tanθ)`

`"LHS" = (secθ  –  sinθ/cosθ)(secθ + tanθ)`

`"LHS" = (secθ  –  tan θ)(secθ + tanθ)  ...[(a + b)(a - b) = a^2 - b^2]`

`"LHS" = sec^2θ  –  tan^2θ      ...{(1 + tan^2θ = sec^2θ),(∴ sec^2θ − tan^2θ = 1):}`

LHS = 1

RHS = 1

LHS = RHS

Hence proved.

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Chapter 6: Trigonometry - Problem Set 6 [Page 138]
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