Question

a man in a Boat roving away from a Lighthouse 100m high takes 2 minutes to change the angle of elevation of the Lighthouse from 60° to 45°. find the speed of boat.​

Answer 1

Answer:

diagram: light house-ab

               60 degree bc(x) and 45 dergree cd(y)

                line joinig ac

                  (having 2 triangles abc and acd)

proof:

speed= distance/time    -1

In tri abc:

        tan60= 100/x

x=100root3/3                  -2

in tri abd

        tan45= 100/x+y

         x+y= 100

             y=100-x

             y=100-100root3/3           (from2)

             y=300-100root3/3

            y=127/3=42.3

As y is the distance

    time is 2min

   subs in (1)

Speed = 42.3/2*60    (min-sec)

            =42.3/120

            =3.525

            =3.5m/sec

PLS LEMME KNOW IF ITS THE RGHT ANS!✌