SOLUTION: I have a right triangle. a=2 and b=4 what does Cos(A)=? I am having trouble with the problem. I know Cos(A)= b/c so i have to figure out what c= i believe? Thanks for the help.

Algebra ->  Trigonometry-basics -> SOLUTION: I have a right triangle. a=2 and b=4 what does Cos(A)=? I am having trouble with the problem. I know Cos(A)= b/c so i have to figure out what c= i believe? Thanks for the help.       Log On


   

Question 86487: I have a right triangle. a=2 and b=4 what does Cos(A)=?
I am having trouble with the problem. I know Cos(A)= b/c so i have to figure out what c= i believe? Thanks for the help.
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
I have a right triangle. a=2 and b=4 what does Cos(A)=?
I am having trouble with the problem. I know Cos(A)= b/c so i have to figure out what c= i believe? Thanks for the help

Yes, you have to calculate c using the Pythagorean theorem:
c%5E2 = a%5E2 + b%5E2
c%5E2 = 2%5E2 + 4%5E2
c%5E2 = 4 + 16
c%5E2 = 20
c = sqrt%2820%29
c = sqrt%284%2A5%29
c = 2sqrt%285%29


so cos(A) = b%2Fc = 4%2F%282sqrt%285%29%29 = 2%2Fsqrt%285%29 = %282%2Asqrt%285%29%29%2F%28sqrt%285%29sqrt%285%29%29 = 2sqrt%285%29%2F5