Question 1

Which rule should be used to find a side when two angles and one side of a triangle are known?

Accepted Answer

The sine rule — The sine rule, a/sin(A)=b/sin(B)=c/sin(C), is used when two angles and one side are known.

Question 2

State the area rule formula for the area of a triangle using two sides a, b and the included angle C.

Accepted Answer

Area = (1/2)ab.sin(C) — The area rule states Area = (1/2)ab.sin(C), using two sides and their included angle.

Question 3

In triangle ABC, a=7, b=9, and angle C=60 degrees. Use the cosine rule to find c^2. (cos60 degrees=0.5)

Accepted Answer

67 — c^2 = a^2+b^2-2ab.cos(C) = 49+81-2(7)(9)(0.5) = 130-63=67.

Trigonometry

Sample practice questions