In the triangle ABC, AB = 12 cm and AC = 10 cm, and ∠ BAC = 60°. What is the value of the length of the side BC ?
Answer & explanation
Correct answer: option 4
We have a concept ,
According to the law of cosine, if a, b, and c are three sides of a triangle ΔABC and ∠A is the angle between AC and AB then, a2 = b2 + c2 - 2bc × cos∠A
AB = 12 cm
AC = 10 cm,
∠BAC = 60°.
BC2 = AB2 + AC2 - 2 × AB × AC × cos60°
= BC2 = 122 + 102 - 2 × 12 × 10 × \(\frac{1}{2}\)
= BC2 = 124
= BC = 11.13