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If 12 cotθ = 13, find the value of 2 sin θ cos θ cos 2 θ − sin 2 θ . - Mathematics

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Question

If 12 cotθ = 13, find the value of `(2sinθ  cosθ)/(cos^2θ - sin^2θ)`.

Sum

Solution

cot θ = `(13)/(12)`

⇒ `cosθ /sinθ  = (13)/(12)`

⇒ `"Base"/"Hypotenuse" xx "Hypotenuse"/"Perpendicular" = (13)/(12)`

⇒ `"Base"/"Perpendicular" = (13)/(12)`
Hypotenuse
= `sqrt(("Perpendicular")^2 + ("Base")^2`
= `sqrt((12)^2 + (13)^2`
= `sqrt(144 + 169)`
= `sqrt(313)`

`(2sinθ  cosθ)/(cos^2θ - sin^2θ)`

= `(2 xx 12/sqrt(313) xx 13/sqrt(313))/((13/sqrt(313))^2 - (12/sqrt(313))^2`

= `(312/313)/(169/313 - 144/313)`

= `(312/313)/(25/313)`

= `(312)/(25)`.

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Reciprocal Relations
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Chapter 26: Trigonometrical Ratios - Exercise 26.1

APPEARS IN

Frank Mathematics [English] Class 9 ICSE
Chapter 26 Trigonometrical Ratios
Exercise 26.1 | Q 36
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