Here is a triangle with the height on the side of the triangle. Use the formula: (1/2)*(Base)*(Height) to find the area of the triangle at the left.

(If one square on the graph = one centimeter)
b = 10cm
h = 10cm
Area
[tex] = \frac{1}{2} \times b \times \: h[/tex]
[tex] = \frac{1}{2 } \times 10 \times 10[/tex]
[tex] = \frac{1}{2} \times 100[/tex]
[tex] = 50 {cm}^{2} [/tex]