55^2 = 50^2 + 35^2 - 2 (50) (35) cos (A)

A = 78.46

Step-by-step explanation:

55^2 = 50^2 + 35^2 - 2 (50) (35) cos (A)

3025 = 2500 + 1225 - 3500 cos A

- 3500 Cos A = - 3725 + 3025

-3500 cos A = - 700

cos A = - 700/-3500

= 0.2

A = cos^-1 0.2

A = 78.46

A=78.46° (to 4sf)

Step-by-step explanation:

The only way to approach this problem is to solve the equation.

55²=50²+35²-2 (50) (35) cos (A)

3025=2500+1225-3500cosA

3025=3725-3500cosA

Now collecting like terms together:

3025-3725=-3500cosA

-700=-3500cosA

CosA=0.2

A=78.46° (to 4sf)