3^2 = 1^2 + 2^2 - 2(1)(2)CosB

I guess we're solving for angle B. I think we can easily reduce to -1 = CosB. So how do you solve for B? Calculator? How?

B is pi radians or 180 degrees

Thanks Crom.

Have you tried to look at it graphically? Represent cos(x) as a graph?
You can see that Cos(x)= -1 at -Pi or -180 degrees.


-k

My lovely wife says you can use the unit circle to find the answer or you can find the inverse cosine of -1 using your calculator.

I broke a sweat just reading the question.

Cos^-1 is a function on most scientific calculators, defiantly on graphing calculators.

realcalc for android is what I use anymore -no idea where my Ti89 got off to.
shft+cos is the cos^-1 button on it.

I don't even know what button to press om my watch calculator for this.