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If 4sinθ = √ 13 , find the value of 4 sin θ − 3 cos θ 2 sin θ + 6 cos θ - Mathematics

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प्रश्न

If 4sinθ = `sqrt(13)`, find the value of `(4sinθ - 3cosθ)/(2sinθ + 6cosθ)`

योग

उत्तर


Consider ΔABC, where ∠B = 90°

⇒ 4sinθ = `sqrt(13)`

⇒ 4sinθ = `sqrt(13)/(4)`

⇒ sinθ = `"Perpendicular"/"Hypotenuse" = "BC"/"AC" = sqrt(13)/(4)`

By Pythagoras theorem,
AC2 = AB2 + BC2
⇒ AB2 
= AC2 - BC2
= `4^2 - (sqrt(13))^2`
= 16 - 13
= 3
⇒ AB = `sqrt(3)`
Now,

cosθ = `"Base"/"Hypotenuse" = "AB"/"AC" = sqrt(3)/(4)`

`(4sinθ - 3cosθ)/(2sinθ + 6cosθ)`

= `(4 xx sqrt(3)/(4) - 3 xx sqrt(3)/4)/(2 xx sqrt(13)/4 + 6 cc sqrt(3)/4)`

= `((4sqrt(13) - 3sqrt(13))/(4))/((2sqrt(13) + 6sqrt(13))/(4)`

= `(4sqrt(13) - 3sqrt(13))/(2sqrt(13) + 6sqrt(13)`

= `sqrt(13)/(8sqrt(13)`

= `(1)/(8)`.

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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 27.1
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