SOLUTION: I have a triangle that has two 18' sides and one 20' side. I would like to know what the angle opposite the 20' side is. Thank you.

Algebra ->  Triangles -> SOLUTION: I have a triangle that has two 18' sides and one 20' side. I would like to know what the angle opposite the 20' side is. Thank you.       Log On


   

Question 855788: I have a triangle that has two 18' sides and one 20' side. I would like to know what the angle opposite the 20' side is. Thank you.
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
This is a side-side-side(SSS) triangle problem
We use the law of cosines to find the angle opposite the 20' side
cos(x) = (18^2 + 18^2 - 20^2) / (2 * 18 * 18)
cos(x) = 0.38
arccos (0.38) = 67.5 degrees
therefore, the angle opposite the 20' side is 67.5 degrees