Question

question 4 of 10
what is cos 45°?
a. $\frac{1}{2}$
b. $sqrt{2}$
c. $\frac{1}{sqrt{2}}$
d. 1

Explanation:

Step1: Recall cosine definition

The cosine of an angle in a right - triangle is defined as $\cos\theta=\frac{\text{adjacent}}{\text{hypotenuse}}$.

Step2: Identify sides for 45 - degree angle

For a $45^{\circ}$ angle in the given right - triangle, the adjacent side to the $45^{\circ}$ angle has length 1 and the hypotenuse has length $\sqrt{2}$. So, $\cos45^{\circ}=\frac{1}{\sqrt{2}}$.

Answer:

C. $\frac{1}{\sqrt{2}}$