Concept:Use trigonometry in the right triangle formed by the broken tree to relate the height of the break point to the fallen part.Explanation:Let x be the height of the point where the tree is broken from the ground.Let y be the length of the broken part that falls to the ground.Total height of the tree is 30 m, so:x+y=30The fallen part makes an angle of 30∘ with the ground.In the right triangle, sin30∘=yx.Since sin30∘=21, we get:yx=21⇒y=2xSubstitute y=2x into x+y=30:x+2x=303x=30x=10 m