SOLUTION: I am trying to use law of cosines, but I keep going wrong somewhere. I know sides c=90in and b=45in and the angle A=30. Please help me fill out the rest of the triangle! Thanks!

Algebra ->  Trigonometry-basics -> SOLUTION: I am trying to use law of cosines, but I keep going wrong somewhere. I know sides c=90in and b=45in and the angle A=30. Please help me fill out the rest of the triangle! Thanks!      Log On


   

Question 954939: I am trying to use law of cosines, but I keep going wrong somewhere. I know sides c=90in and b=45in and the angle A=30. Please help me fill out the rest of the triangle! Thanks!
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
Law Of Cosines, c%5E2%2Bb%5E2-2cb%2Acos%28A%29=a%5E2;

Symmetric Property and substitute given values, a%5E2=90%5E2%2B45%5E2-2%2A90%2A45%2Acos%2830%29;

Evaluate or compute, and find square root of a%5E2.

a=sqrt%2890%5E2%2B45%5E2-2%2A90%2A45%2Acos%2830%29%29




Study the form of the formula carefully, and you should be able to make two other equations.

One of them, a%5E2%2Bb%5E2-2ab%2Acos%28C%29=c%5E2.