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Chapter: Trigonometry· Mathematics Part 2 (Geometry)

Asked in: March 2025 board paper (same type, 80 m and 45° for a church, in June 2026)An observer at a distance of 10 m from a tree looks at the top of the tree; the angle of elevation is 60°. To find the height of the tree complete the activity. (\(\…

Asked in: March 2025 board paper (same type, 80 m and 45° for a church, in June 2026)

An observer at a distance of 10 m from a tree looks at the top of the tree; the angle of elevation is 60°. To find the height of the tree complete the activity. (\(\sqrt3 = 1.73\))

[Figure: AB = h is the tree, B its foot; C is the observer with BC = 10 m; \(\angle BCA = 60^\circ\).]

Activity: \(\tan\theta = \dfrac{\text{____}}{BC}\) ...(I) \(\tan 60^\circ = \text{____}\) ...(II)

\(\dfrac{AB}{BC} = \sqrt3\) (from (I) and (II)) \(AB = BC \times \sqrt3 = 10\sqrt3\)

AB = 10 × 1.73 = ____ \(\therefore\) height of the tree is ____ m.

1 answer

Best answer

Answer: Height of the tree = 17.3 m

In right-angled ΔABC, \(\tan\theta = \dfrac{AB}{BC}\) ...(I) and \(\tan 60^\circ = \sqrt3\) ...(II).

\(\therefore \dfrac{AB}{10} = \sqrt3\) \(\therefore AB = 10\sqrt3 = 10 \times 1.73 = 17.3\)

Blanks: AB; \(\sqrt3\); 17.3; 17.3.

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