idk

Oops.

sin(theta) bigger than 1 is impossible xD

'theta'   is gennerally used as an unknown angle   like   sin(theta) = 2/3      much the way 'x' is used as an unknown variable in an equation: x + 3 = 5

Theta is a Greek letter.

Summarizing the 2 answers above:

Theta is a Greek letter which can represent an unknown angle 

Example :$sin \theta = \frac{3}{2}$