Question

If $\Delta ABC$ is right angled at C, then cos B = ___.

• A. $\frac{AC}{AB}$
• B. $\frac{AC}{BC}$
• C. $\frac{AB}{BC}$
• D. $\frac{BC}{AB}$

Answer 1

The correct option is D $\frac{BC}{AB}$

The cosine of an angle is the ratio of the length of the adjacent side to the length of the hypotenuse.

$\Delta ABC$ with the right angle at C is the one shown in the below figure.

$cosB=\frac{\text{Adjacent side}}{\text{Hypotenuse}}=\frac{BC}{AB}$