negative powers 8051
Negative powers are equal to the inverse of the original to the power of the absolute original value. That is to say:

x^-y = 1/x^y

With regards to inverse trigonometric functions, the inverse of a function is also known as the arc of it. eg;
sin^-1 = asin
cos^-1 = acos
tan^-1 = atan

Thanks to Chris Stratton for that helpful reminder!