Question

How to solve for a missing side length of a triangle (NOT a right triangle) when one side is 4m and another side is 3m, and the only angle is 120 degrees?

Answer 1

Answer:

c ≈ 6.08 m

Step-by-step explanation:

Your question is how to solve for a missing side length of a triangle when given 2 sides length and an angle. The side length can be solved using the cosine rule . We use cosine rule to find the length of a side of a triangle when given two sides and an included angle.

The cosine rule formula for finding a side length are as follows

c² = a² + b² - 2ab cosC

b² = a² + c² - 2ac cosB

c² = a² + b² - 2ab cosC

Using cosine rule

c² = 4² + 3² - 2 × 4 × 3 cos 120°

c² = 16 + 9 - 24 cos 120°

c² = 25 - 24 (-0.5)

c² = 25 + 12

c² = 37

square root both sides

c = √37

c = 6.0827625303

c ≈ 6.08 m