Every trigonometric arc function has two values. For example, the arc sine of .5 is 30° or 150°. Sometimes we can determine which is the correct value to use but other times it is not so obvious. Is there any rule about this second trigonometric arc function?

Question

Every trigonometric arc function has two values.  For example, the arc sine of .5 is 30° or 150°.  Sometimes we can determine which is the correct value to use but other times it is not so obvious.  Is there any rule about this second trigonometric arc function?

anonymous · Answer

Quadrant can be given to you, such as

90 degree < theta < 180 degrees

anonymous · Answer

150 degrees is a reference angle to 30 degrees, since 150+30=180 (degrees).  

Depending on what quadrant you are in, sine may be negative or positive.  150 degrees would be present in an obtuse triangle,  because it has an angle greater than 90 degrees.

anonymous · Answer

so like trig inverse functions?