SOLUTION: Calculate angle A given the following information about triangle ABC. Calculate the side c using Cosine Law. a=12, b=14, c=20 (there is exponent 0 beside the 20) Thank you.

Algebra ->  Trigonometry-basics -> SOLUTION: Calculate angle A given the following information about triangle ABC. Calculate the side c using Cosine Law. a=12, b=14, c=20 (there is exponent 0 beside the 20) Thank you.      Log On


   

Question 563799: Calculate angle A given the following information about triangle ABC. Calculate the side c using Cosine Law.
a=12, b=14, c=20 (there is exponent 0 beside the 20)
Thank you.
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
You should know enough about angles to interpret "c=20" as "20 degrees" not "20^0."

Draw the figure and label the sides/angles first. Then you can find side c using the cosine rule (also known as law of cosines)



You can find c from there. You can't really use the law of cosines on angle A, but you can use the law of sines:



You know a = 12, C = 20 degrees, and you would have already found c. Hence replace these in to evaluate sin A, then take the arcsine of both sides.