If you were to calculate the EXACT number, the cosine of theta would be rad.15 over 4.
Sine is opposite over hypotenuse, so the opposite would be 1 and the hypotenuse would be 4. Using the Pythagorean Theorem, you will see that the last side to your triangle is the square root of 15 (AKA rad.15). Cosine is adjacent over hypotenuse, thus rad.15 over 4.
