I'm learning physics, and I'm reviewing over the trig part of the chapter. My professor does not allow us to use calculators. I'm looking at the inverse of the trig functions. What I don't understand is : it says that the reciprocal does not equal the inverse. like tan -1 does not equal 1/tan. So how do you figure this out without a calculator. I was looking also to see if cos would be hyp/adj instead of adj/hyp but this also is not the way it is in the book. Will someone help me ? Maybe this is a better example. There is an example in my book. A lakefront drops off gradually an an angle theta. For safety reasons it is necessary to know the depths of the lake at various distances from the shore. To get this information a lifeguard rows out from the shore a distance of 14.0m and drops a weighted fishing line. By measuring the length of the line he determines the depth to be 2.25m what is the value of thea ? so it shows the answer is theta = tan^(-1) (2.25m/14.0m) = 9.13 degrees. How would you have known enough to use the inverse ? Why couldn't you just use tan instead of the inverse ? it's hard to explain what the picture looks like, but is it because the surface of the lake is given and considered the adjacent rather than the hypotenuse ? ThaNKs !