SOLUTION: Solve the triangle using the given information. a=7cm b=4cm c=5cm How do I find the angles? Law of cosines? Please provide all steps.

Algebra ->  Trigonometry-basics -> SOLUTION: Solve the triangle using the given information. a=7cm b=4cm c=5cm How do I find the angles? Law of cosines? Please provide all steps.      Log On


   

Question 684448: Solve the triangle using the given information.
a=7cm
b=4cm
c=5cm
How do I find the angles? Law of cosines?
Please provide all steps.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
a^2 = b^2 + c^2 - 2*b*c*cos(A)

49 = 4^2 + 5^2 - 2*4*5*cos(A)

49 = 16 + 25 - 40*cos(A)

49 = 41 - 40*cos(A)

49 - 41 = -40*cos(A)

8 = -40*cos(A)

8/(-40) = cos(A)

-1/5 = cos(A)

cos(A) = -1/5

A = arccos(-1/5)

A = 101.536959

So the angle A is roughly 101.536959 degrees.

I'll let you find angles B and C