Question

from the point bridge across a river ,the angle of depression of the blanks on opposite sides of the river are 30° and 45° respectively. if the bridge is at a height of 30m from the water level ,then find the width of the river. (use √3=1.73)​

Answer 1

Answer:

length of witth of river = AB

and bridge is at height of 3m

So DP =3m

Angel on the opposite side of river are

30° 45°

so QPA = 30°

RPB =45°

We need to find AB = ?

PDA =PDB =90°

PAD= QPA=30° (alternative angle)

QPB =PBD=45° ( alternative angle)

Now in triangle PBD

Tan =45°= PD upon DB

1=3 upon DB

DB =3

=AB=AD+PB

=3√3+3

3(√3+1

hence width of river is 3(√3+1