Hello, I'm trying to solve this equation. (4-4cos(∏*0.16*4)) - (4-4cos(∏*0.16*3)) It seems like it should be so easy. First I start with the left hand side (∏*0.16*4). Then I take the cosine of that, and then multiply it by 4. Then I do 4 - [answer] to get a value for the full left side (0.00246263391564268270661821942049). Then I do the same thing with the right side. (∏*0.16*3) and take the cosine of that. Multiply it by 4 and subtract that answer from 4 for a right side value of 0.00138529377181347385337035623753. Then I subtract the right side from the left side.. 0.00246263391564268270661821942049 - 0.00138529377181347385337035623753 = 0.00107734014382920885324786318296 But this is far from the right answer, which is supposed to be roughly 1.95. I don't know what I'm doing wrong. I've tried degrees, radians, gradients. I've tried changing the order in which I multiply everything but nothing seems to get me to the right answer. Even wolfram alpha tells me the right answer, but it doesn't explain HOW it gets that answer. image hosting I'm going crazy because I can't figure this out. I suspect that I'm not processing cosine right somehow, but I really have no idea what the right way should be. I thought it is just the cosine of the product of everything in the parenthesis. I don't think it's a calculator error. I'm mainly using the calculator on Windows 7 but I tried it also on a handheld calculator and still get the same answer.