Let the height of the triangle ( the tree part thats still standing ) be 10m
angle of elevation= /_ 30
using sin 30= 1/2
(sin 0= opp/hypo)
sin 30= 10/hypo
1/2=10/hypo
cross multiplying,
hypo = 20 m
Hypo is nothing but the broken part of the tree, so adding the height of triangle and the hypotenuse,
we get the complete height,
10+20= 30 m ans.
hope it helped ( also that its right ;) )
regards