Inputting this function of x into the nth Chebyshev polynomial of the first kind yields this function of nx. This function equals the average of e to the ix and e to the minus ix, and (10[1])the hyperbolic form of this function is the average of e to the x and e to the minus x. The first two terms of this function’s Taylor series (-5[1])are (10[1])one and minus one-half x-squared. For a complex number of (10[1])modulus one, this function of the argument is the number’s real part. Pythagoras’ (-5[1])theorem is a special case of a law named after this (10[1])function. (10[1]-5[2])The reciprocal of this function is secant. For 10 points, name this trigonometric function that (10[1])equals adjacent (10[1])over hypotenuse in a right triangle. (10[1])■END■ (10[1])