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