In a ΔABC right angled at B, if BC = 4 cm and ∠C = 60°, then length of AC is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 8 cm
In a right triangle, the cosine of an angle is the side next to it divided by the hypotenuse. The right angle is at B, so AC is the hypotenuse and BC is the side next to angle C.
\(\displaystyle \cos C=\frac{BC}{AC}\), so \(\displaystyle \cos60^\circ=\frac{4}{AC}\)
\(\displaystyle \frac{1}{2}=\frac{4}{AC}\), so \(AC=8\) cm