In a triangle ABC, the AC side is a, the angle A = alpha, the angle B = beta. Find the area of the triangle.

Using the sine theorem, we define the length of the BC side.

BC / Sinα = AC / Sinβ.

ВС = AC * Sinα / Sinβ = a * Sinα / Sinβ.

Angle АСВ = (180 – (α + β)).

Then, the area of the triangle ABC will be equal to:

Sас = АС * ВС * SinACB / 2 = a * (a * Sinα / Sinβ) * Sin (180 – (α + β)) / 2 = a2 * Sinα * Sin (α + β) / 2 * Sinβ.

Answer: The area of a triangle is a2 * Sinα * Sin (α + β) / 2 * Sinβ.



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