question_answer

At any point P on the ground the angles of elevation of the top of a 10 m high building and that of a helicopter flying just over the building are \[30{}^\circ \]and \[60{}^\circ \] respectively. Find the height of the helicopter from the earth. (Given, \[\sin 30{}^\circ =\frac{1}{2},\cos 30{}^\circ =\frac{\sqrt{3}}{2}\])

A)  \[10\sqrt{3}\,\,m\]         

B)  20 m

C)  \[\frac{30}{\sqrt{3}}\,\,m\]       

D)  30 m