cos(x) from Its Series, With and Without the Library

Read a real number x in radians and an integer N, sum the first N terms of the series cos x = 1 - x^2/2! + x^4/4! - x^6/6! + ..., and print two lines: series cos(x) = 0.540302 with the sum, and library cos(x) = 0.540302 with the value from cos in <math.h>, both to six decimal places. Build each term from the previous one, term = -term * x * x / ((2k + 1)(2k + 2)) for k from 0, rather than computing powers and factorials. N must be between 1 and 100; otherwise print N must be between 1 and 100 and return 1. If x and N cannot be read, print invalid input and return 1.