In a triangle measure of two sides is 6 cm and 4 cm and the common angle of these two sides is 60°. Find the third side (in cm)?
Explanation:
We can apply the cosine rule to find the third side.
AC2 = AB2 + BC2 - 2 × AB × BC × CosB
Here, AB = 6, BC = 4 and ∠B = 60°
⇒ AC2 = 62 + 42 - 2 × 6 × 4 × Cos60°
⇒ AC2 = 36 + 16 - 2 × 6 × 4 × 1/2 [Cos60° = 1/2]
⇒ AC2 = 36 + 16 - 6 × 4
⇒ AC2 = 28
⇒ AC = 2√7
Hence, option (c).
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