中等MATH-TRIG-006
The angle of elevation of the top of a tower, from a point 40 m from its foot on level ground, is 30°. What is the height of the tower?
A. 40/√3 m✓ 答案
B. 40√3 m
C. 20 m
D. 40 m
解說
The ground distance is adjacent to the angle, so height = 40 tan 30° = 40/√3 m. The value 40√3 m uses tan 60°, which swaps opposite and adjacent. The value 20 m is 40 sin 30°, treating 40 m as the hypotenuse.