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If cotθ = √ 7 , show that cosec 2 θ − sec 2 θ cosec 2 θ + sec 2 θ = 3 4 - Mathematics

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प्रश्न

If cotθ = `sqrt(7)`, show that `("cosec"^2θ -sec^2θ)/("cosec"^2θ + sec^2θ) = (3)/(4)`

योग

उत्तर

cotθ = `sqrt(7)`

⇒ `cosθ/sinθ = sqrt(7)`

⇒ `"Base"/"Hypotenuse" xx "Hypotenuse"/"Perpendicular" = sqrt(7)/(1)`

⇒ `"Base"/"Perpendicular" = sqrt(7)/(1)`

Hypotenuse
= `sqrt(("Perpendicular")^2 + ("Base")^2`
= `sqrt(1 + 7)`
= `2sqrt(2)`

To show: `("cosec"^2θ -sec^2θ)/("cosec"^2θ + sec^2θ) = (3)/(4)`

`("cosec"^2θ -sec^2θ)/("cosec"^2θ + sec^2θ)`

= `(("Hypotenuse"/"Perpendicular")^2 - ("Hypotenuse"/"Base")^2)/(("Hypotenuse"/"Perpendicular")^2 + ("Hypotenuse"/"Base")^2)`

= `((2sqrt(2)/1)^2 - (2sqrt(2)/sqrt(7))^2)/(((2sqrt(2))/1)^2 + (2sqrt(2)/sqrt(7))^2`

= `(8/1 - 8/7)/(8/1 + 8/7)`

= `((56 - 8)/7)/((56 + 8)/7)`

= `(48)/(64)`

= `(3)/(4)`.

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अध्याय 26: Trigonometrical Ratios - Exercise 26.1

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फ्रैंक Mathematics [English] Class 9 ICSE
अध्याय 26 Trigonometrical Ratios
Exercise 26.1 | Q 34
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