General solution of cos q = k
Method I
Let a be the least positive angle such that
Method II
Let a be the smaller positive angle with cos a = k.
Then, cos(-a) = k
cos q = cos a and cos (-a)
A = q or - a
Also, any co-terminal angle with above is trigonometrically equivalent and so has the same cosine.
q = (Any even multiple of p)+ a or (Any even multiple of p) - a
Particular Cases
ii) If cos q = 1, then cos a = 1, a = 0
= even multiple of p
