Question

A man in a boat rowing away from a light house 100m height , takes 2 min too change the angle of elevation of top of the light house from 60° to 45° find speed of boat..???.. please help me i am in exam hall..

Answer 1

Height of the Light house , p = 100 m

let initial distance be x m

and the angle is 60°

so, tan60° = p/x = 100/x

or, √3 = 100/x

or, x = 100/√3 m

Now after time 2min let the new distance be y

and angle is 45°

so, tan45° = 100/y

so, 1 = 100/y

so, y = 100 m

So, distance travelled in 2min

= y - x = 100 - 100/√3 = 100 - 57.737

= 42.263 m

So, d = 42.263 m

t = 2 min = 2×60 = 120 sec

speed = d/t = 42.263/120 m/s

= 0.35219 m/s

Going away from the light house with a speed of 0.35219 m/s.

Answer 2

Answer:

Step-by-step explanation:

Refer to the attachment