Question

In the diagram below, if the measure of < C = 45 °, and side AC = 10, then side BC = _____.

Answer 1

Solution:

Given:

Using the trigonometric ratio of cosine,

$\begin{gathered} cos\theta=\frac{adjacent}{hypotenuse} \\ cos45=\frac{BC}{10} \\ BC=10\times cos\text{ 45} \\ BC=10\times\frac{\sqrt{2}}{2} \\ BC=5\sqrt{2} \end{gathered}$

Therefore, OPTION A is correct.