Definition: An equation on consisting of the trigonometric functions of a variable angle θ  R is called a 'trigonometric equation'

Canonical equation:
Def: The equation of the form f(x) = k when f(x) = sin x, cos x or tan x is called a 'canonical equation'., Canonical equations have 'principle solutions'.
        Every trigonometric equation can be reduced to one or more canonical equations.
Solution
        The values of the variable angle θ, that is any number θ, satisfying the given trigonometric
         equation is called a 'solution' of the equation. The set of all solutions of a trigonometric equation is called the 'solution set' of the equation.
          A 'general solution' of a trigonometric equation is of the form θ₀ + f(n) where θ₀ is a
particular solution and f(n) is function if n ∊ Z involving π.