How do we calculate the area of rectangles and triangles?

Rectangles: Base* Height is the formula to find the area of rectangles
Triangles: Base*Height/ 2 this is the formula to find the area of triangles

Triangle area conjecture:
The area of a triangle is given by the formula A=1/2(B*H) where A is the area, B is the length of the base and H is the height of the triangle.