Let SQ = h be the tower. ∠SPQ = 30° and ∠SRQ = 60° The length of shadow is 50 m long hen angle of elevation of the sun is 30° than when it was 60°. So, PR = 50 m and RQ = x m So in ∆SRQ, we have `tan 60^circ = h/x` .......`[because tan theta = "perpendicular"/"base" ⇒ tan 60^circ = (SQ)/(RQ)]` ⇒ `sqrt(3) = h/x` .......`[because tan 60^circ = sqrt(3)]` ⇒ ` x = h/sqrt(3)` In ΔSPQ, `tan 30^circ = h/(50 + x)` .......`[because tan 30^circ = (SQ)/(PQ) = (SQ)/(PR + PQ)]` ⇒ `1/sqrt(3) = h/(50 + x)` .....`[because tan 30^circ = 1/sqrt(3)]` ⇒ `50 + x = sqrt(3)h` Substituting the value of x in the above equation, we get ⇒ `50 + h/sqrt(3) = sqrt(3)h` ⇒ `(50sqrt(3)h)/sqrt(3) = sqrt(3)h` ⇒ `50sqrt(3) + h = 3h` ⇒ `50sqrt(3) = 3h - h` ⇒ `3h - h = 50sqrt(3)` ⇒ `2h = 50sqrt(3)` ⇒ `h = (50sqrt(3))/2` ⇒ `h = 25sqrt(3)` Hence, the required height is `25sqrt(3) m`. |