Inverse Trigonometric FunctionsWhen you are given an angle X, trigonometry is used to compute Sin(X), Cos(X), and Tan(X).  When the value of Sin(X) is given, for example Sin(X) = 0.2, the inverse sine function provides the value of X.  Sin-1(X) is known as the inverse sine function and it is NOT equal to 1/Sin(X).X = Sin-1(0.2) = 11.5°This function is not single valued.  In the range of 0° to 360°, the Sine function is positive in the first and second quadrant.  So, X = 11.5°, but it also equals 180° - 11.5° which is 168.5°.  For more information,  you should inspect the inverse graphs page.When the cosine of angle X is known, such as Cos(X) = 0.2, the inverse cosine function finds the value of X.  Cos-1(X) is known as the inverse cosine function as is NOT equal to 1/Cos(X).  X = Cos-1(0.2) = 78.5°This function is also not single valued, and since cosine is positive in the first and fourth quadrants, the other value would be 360° - 78.5° which is 281.5°.When the tangent of angle X is known, Tan(X) = 0.2, the inverse tangent function can solve for  the value of X.  Tan-1(X) is the known inverse tangent function and is NOT equal to 1/Tan(X).  X = Tan-1(0.2) = 11.3°However, this function is not single valued, and since the tangent function is positive in the first and third quadrants, the other value would be 180° + 11.3° which is 191.3°.