Question

Why does sin 90 degrees equal 1

Answer 1

The sine of an angle is a trigonometric function. It is calculated as the ratio between the longest side(hypotenuse) of a right triangle and the length of the side opposite the given angle. You will then realize that in a right angled triangle, the side that is opposite the angle 90° , is the hypotenuse. This therefore means that you will calculate sine 90° as follows:
  
sine 90° = opposite         = hypotenuse    or opposite      = 1
                 hypotenuse        hypotenuse       opposite