JEE Main 2022 · 29 Jul · Shift 1 · Mathematics Q11

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MathematicsSingle correct+4 / -1Question 11 of 90

The angle of elevation of the top of a tower from a point A due north of it is α and from a point B at a distance of 9 units due west of A is $\cos^{-1}\left(\dfrac3{\sqrt{13}}\right)$ . If the distance of the point B from the tower is 15 units, then cot α is equal to :

\dfrac65

\dfrac95

\dfrac43

\dfrac73

Answer and worked solution

Official answer: A

Ground distances. OB = 15, AB = 9 and OA ⟂ AB, so OA = 12.

Height from B: $\tan=\frac23$ , $h=10$ . So $\cot\alpha=\frac{12}{10}=\frac65$ .

(A)

Topics:Heights and distances

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JEE Main 2022 · 29 Jul · Shift 1, Mathematics question 11