If you know all three sides of a triangle, you can determine the area by applying the following formula:

Where s = 1/2 perimeter of a triangle

For the triangle shown in figure 1-30, the area computation is

When you know two sides of a triangle and the angle included between them, you can determine the area by applying, appropriately, one of the following formulas:

In figure 1-31, two sides, b = 13.00 ft and c = 9.00 ft, and the included angle, A = 4000, are given. The sine of 4000 is 0.64279. The area computation is as follows:

Figure 1-31.-Area of a triangle with two sides and one angle given.