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