9-2

We are in chapter nine in advanced math right now. In section 9-2, we learned how to find the area of a triangle given the lengths of two sides and the measure of the included angle. There are two formulas in this section – one for a right triangle and one for a non-right triangle.

1/2bh – only right triangles
1/2absin(angle b/w) – non right triangles

EXAMPLE 1: Two sides of a triangle have lengths 6 cm and 3 cm. The angle between the sides measures 70 degrees. Find the area of the triangle.
A). First, draw your triangle of course.
B). Label the two sides with 6 cm on one and 3 cm on the other.
C). Since we are not told it is a right triangle, we’re going to use the second formula
(1/2absin(angle b/w).
D). Plug in all of your numbers given. (1/2(6)(3)sin70 degrees)
E). Multiply to get 9sin70 degrees.
F). Your answer is A = 8.46 cm squared

EXAMPLE 2: In triangle ABC b=3, c=5, and a=60 degrees. Find the area.
A). Draw your triangle and label the sides.
B). Plug your numbers into the second formula, since we aren’t told it’s a 90 degree angle.
(1/2(3)(5)sin60 degrees).
C). Your answer is A = 6.5 *We aren’t given any units, so leave it alone.