Question

How do you find the exact value of `cos (pi)`?

Answer 1

`pi=3.14159265...` is a transcendental number. This is a limit problem of `x to pi` of cos x. cos x is continuous at `x = pi`. Both `cos pi_+ and cos pi_( - )` approach to the same limit `-1`.

Explanation:

The Calculator value of `cos pi = cos 180^o = -1` is by truncation

and rounding of (say) 10-sd `-1.000000000` approximation

obtained from an approximating truncated continued fraction of

quadratics.

The error (if any) in the knocked out part of the processed string and i
is hiding..

`180^o` is converted to x = 3.14159263...(truncated) and used in the

approximation process..

Glory to Numerical Analysis Experts of older generation who perfected all these approximations of functions, for use in electronic hand devices..