Recognize Problem: Recognize that the equation sinx=21 is asking for the angle(s) x for which the sine function has a value of 21. We know from trigonometry that the sine function has a value of 21 at specific standard angles.
Recall Unit Circle: Recall the unit circle and the values of sine for standard angles.The sine of an angle is 21 at angles of 30 degrees (6π radians) and 150 degrees (65π radians) in the first and second quadrants, respectively, where the sine function is positive.
Convert Angles: Convert the known angles to radians if necessary.Since the sine function is periodic, we also need to consider all angles coterminal with 30 degrees and 150 degrees.The general solution for x where sinx=21 is x=6π+2nπ and x=65π+2nπ, where n is any integer.