Sin, cos and tan are part of the trigonometric function. Sin is calculated from opposite/hypotenuse, while cos is calculated from adjacent/hypotenuse. There is some formula that can be derived from the equation. One of them is sin (90-x)= cos x If you use it, the calculation would be: sin 49° = cos x sin 49= sin (90-x) 49= 90-x x= 90-49= 41
