14712 - Compute Cosine Function with a Series   

Description

Write a program to compute cos⁡(x) for a given real number x (in radians, 0≤x≤2π) using the Taylor series:

To ensure sufficient accuracy, use double precision floating-point arithmetic and sum the series up to n = 15 (i.e., include the terms for n=0,1,…,15).

For example, please perform this calculation

Information about factorial function:

  • 0! = 1
  • (2n)!=1×2×3×⋯×(2n)

Notes:

  • Do not call a library cosine function to compute the answer; use the series definition.

  • For efficiency and numerical stability, update powers and factorials iteratively rather than recomputing them from scratch each term.

Input

Given real number x (in radians, 0≤x≤2π)

Output

Output: Print the result rounded to exactly 6 digits after the decimal point.

Sample Input  Download

Sample Output  Download




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