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# Definition of Trigonometric Equations

Suppose that given the equation sin2 x + cos2 x = 1 and ask for the value of x that satisfies the equation. It turns out that for each x value it always fulfills. Such an equation is called identity. In trigonometry other than identity there is also a form of equation that only applies to the values ​​of certain variables.

In your school you must have learned about the functions of sine, cosine, and tangent which are periodic functions. An example is a sine function said to have a 360 period, if and only if α0 = sin (α + n . 360)0, n integers. This means that the value of the trigonometric function always repeats every plus or minus multiples of 360. You also know the periods of cosine functions and tangents respectively are 360 ​​and 180. Based on this information, the following rules can be used to solve the trigonometric equation.

1. If sin x0 = sin α0, then x = α + n . 360 or,

x = (180 – α) + n . 360

2. if cos x0 = cos α0, then x = α + n . 360 or,

x = - α + n . 360

3. if tan x0 = tan α0, then x = α + n . 180 with n ∈ interger.

4. if a sin x0 = 0 then x = k . 180

5. if b cos x0 = 0 then x = 900 = ± k . 180

6. if c tan x0 = 0 then x = k . 180 with k ∈ interger.