Originally Posted by

**jwu** Just a simple problem. But I got stuck on some points.

We just learned the law of sine and the law of cosine from class.

And here's the assignment according this two topics:

Solve each triangle. Give lengths to three significant digits and angle measures to the nearest tenth of a degree.

a=8, b=5, ∠C=60°

My solution:

Because we have the condition "SAS". So I used the law of cosine to solve for c.

c²=a²+b²-2abcos 60°

=7

Then all we need to do next is to find the two angles of the triangle, right?

So I used the sine law：

sin C/c=sin A/a

sin 60°/7=sin A/8

sin A= sin 60°*8/7

A= 81.8° and 98.2°

Here's where I got stuck. The answer at the very end of book only shows the answer 81.8°. But I think 98.2° is also acceptable. There should be two possiblities. Can somebody tell me why it doesn't fit?