(First time using this code to draw diagrams)Code:b * /|\ / | \ / |h \ / | \ / | \ a*----------------*c
Lets use this triangle as an example.
h = height
Area of a triangle = 1/2 * base * height
Base = length AC
Height = length AB * sin (angle BAC)
Therefore area of triangle = 1/2 * AC * AB * sin(angle BAC)
I had to prove this when I was learning trigonometry as well.