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If cosB = 1 3 and ∠C = 90°, find sin A, and B and cot A. - Mathematics

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Question

If cosB = `(1)/(3)` and ∠C = 90°, find sin A, and B and cot A.

Sum

Solution

cosB = `"Base"/"Hypotenuse" = "BC"/"AB"`

(AB)2 = (AC)2 + (BC)2
⇒ AC = `sqrt(("AB")^2 - ("BC")^2`
⇒ AC = `sqrt(3^2 - 1)`
= `sqrt(9 - 1)`
= `2sqrt(2)`

sin A = `"BC"/"AB" = "Perpendicular"/"Hypotenuse" = (1)/(3)`

tan B = `"AC"/"BC" = "Perpendicular"/"Base" = 2sqrt(2)`

cot A = `(1)/"tan A" = "BAse"/"Perpendicular" = "AC"/"BC" = 2sqrt(2)`.

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Chapter 26: Trigonometrical Ratios - Exercise 26.1

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Frank Mathematics [English] Class 9 ICSE
Chapter 26 Trigonometrical Ratios
Exercise 26.1 | Q 5
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