I don't know what is meant by 'standard position' but I'm assuming that the angle is restricted to Quadrant I.
If you recall the definition that , then you can draw a right angled triangle with a base of 12 and a height of 5 with as your angle.
Recall that . We already have the 'opposite' side, i.e. 5. We just need the hypotenuse which you can easily calculate with Pythagoras' Theorem.