what is sin^-1?

$$You use inverse trig when you need to find an angle.\\\\ $sin^{-1}(0.8)$ means find the angle (I'll call it $\theta$ where $sin\theta = 0.8$)\\\\ Then as Aziz said \\ inverse sine is the same as arc sine\\ $sin^{-1}$ is the same as asin.$$    

sin^-1 is the same as arcsin or "asin" found on the calculator on the homepage.