Question

If angle of elevation of sun changes from 30° to 60°. Then at these angles of elevation find the difference in the length of shadow of 15 m high pillar.

Answer 1

Let AD is a pillar of height = 15 m

The angle of elevation from point B of ground is 30° and angle of elevation from point C is 60°.

∠ABD = 30° and ∠ACD = 60°

From right angled ∆ADC

From right angled ∆ADB

tan 30° = AD/BD

⇒ 1/√3 = 15/BD

⇒ BD = 15√3 m

Difference in length of shadow = BC

= BD – CD

= 15√3 – 5√3

= 10√3 m

= 10 × 1.732

= 17.32 m

Hence, difference in length of shadow = 17.32 m