



 
Ruby, I presume you mean that x is in the interval [0°,180°]? Please don't use the equals sign except to express that the things on opposite sides of it are equal! It leads to confusion. There is a related class of problems you CAN solve. If you had wanted to solve [say] arctan(x) = arccos(0.5) you could do so by labelling the sides of a right triangle so the cosine of the angle is (0.5)  eg, hypotenuse = 1, adjacent side 0.5; thus opposite side = ?; tangent = ?. You will just have to evaluate arctan(cos(100)); Google can do this for you. Good Hunting!
 


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