Find the area k of the triangle.

**Solution:-**

To find the area of the triangle, use the following theorem.

The area K of a triangle equals one-half the product of two of its sides times the sign of their included angle.

According to this theorem, the formula K = ac sin B can be used to find the area of the triangle specified in the problem statement.

Using the formula K = ac sin B with a = 4, c = 9, B = 40° given the following result.

K = ac sin B

= * 4 * 9 sin 40°

Simplify the right side to find the area of the triangle.

K 11.57 square units.