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