The area of a triangle

According to Heron's formula

S=√p⋅(p-a)⋅(p-b)⋅(p-c)

Where p = (a+b+c) / 2 - semiperimeter of triangle; a,b,c - sides of triangle.

Through the base and the height

S = a ⋅ h / 2

Where a is the base of the triangle; h is the height of the triangle.

Across two sides and an angle

S = a ⋅ b ⋅ sin(a) / 2