Finding the Third Side of Triangle Using Law of Cosines

Triangle QRS has two sides measuring 7 cm and 9 cm. The angle between these two sides is $60^ ext{o}$. What is the length of the third side of the triangle?

To find this, you can use the Law of Cosines, which states:

$$c^2 = a^2 + b^2 - 2ab imes ext{cos}(C)$$

where:

• c is the length of the side opposite angle C
• a and b are the lengths of the other two sides
• C is the measure of the angle between sides a and b