中等math-u07-d03
Two sides of a triangle are b and c and the included angle is A. The area of the triangle is:
A. (1/2)bc sin A✓ 答案
B. bc cos A
C. (1/2)(b + c)A
D. (1/2)a^2
解說
The area formula needs two sides and the angle between them: A = 1/2 bc sin A. The other forms mix in quantities that are not needed.