As the other anwsers show the standard way to cope with this is to place circ between dollar signs. Now if you need to add normal text into a formula or even write a formula using words you can do this with the text-command inside the math-environment. U_2 textrmSecond element of the sequence u_n u_2 textrmSecond.
Letters are printed in italics with more space left.
Hyperbolic functions The abbreviations arcsinh arccosh etc are commonly used for inverse. The second one is used to write expressions that are not part of a text or paragraph and are therefore put on separate lines. For 99 of applications Werners answer is good enough. For me text should only have portions of text that because of its nature within display math cant be typed naturally.