As shown in the figure, Xiaoli, whose height is 1.75m, measured the height of a tree (∠ A = 30) with two triangular rulers with acute angles of 30 and 60 respectively, and we know that she is one of the trees.
Solution: In Rt△ADC.
∫∠A = 30，AD=5m
∴ Tana = CD/AD = (√ 3)/3m
∴cd=ad*tana=5(√3)/3·m
∫ ad =1.75m.
∴CE=AD+DE=4.63m≈4.6m
This tree is about 4.6 meters high.