1. ## trig exact values

Please help me with finding trig exact values. I have always relied on my calculator to give me answers for these problems but now my prof. makes us use a calculator that cant convert decimals to fractions. I know how to do it with easy values when using the special triangles but what do I do when you have something like:

Find the exact value for cos(4/5)

2. ## Re: trig exact values

Originally Posted by jmanna98
Please help me with finding trig exact values. I have always relied on my calculator to give me answers for these problems but now my prof. makes us use a calculator that cant convert decimals to fractions. I know how to do it with easy values when using the special triangles but what do I do when you have something like:

Find the exact value for cos(4/5)
Sorry but that makes no sense, your calculator can tell you what cos(0.8) is can't it?

It will also let you enter cos(4/5) directly

CB

3. ## Re: trig exact values

sorry the question is arccos(4/5), therefore cos(theta)=4/5. How would I find the angle?

4. ## Re: trig exact values

Originally Posted by jmanna98
sorry the question is arccos(4/5), therefore cos(theta)=4/5. How would I find the angle?
Think 3,4,5 triangle, and there is no "exact" value of arccos(4/5).

CB