A bridge across a river makes an angle of 45 degree with the bank of river if the length of the bridge across the river is hundred metre find the width of the river

Let AB = the width of the river and 

AC =  the length of the bridge across the river. 

The bridge AC makes and angle 45° with the river bank.

∴ AC = 100 m and ∠CAB = 45°.

In ΔBAC,

Thus, the width of the river is