Question

A triangle has base 6 cm and an area of 12 sq. cm. The difference of the base angles is 60°. Prove that the angle opposite is given by the equation

8 cos A - 6 cos A = 3

Answer 1

We have B + C = 180° − A ; B − C = 60°. Therefore,

⇒ 4cosA = 3(cosA - cos120°)  = 3 cos A + 3/2

⇒ 8cos A – 6cos A = 3