How is it possible to have sin of angle greater than 90 degrees. if sin is ratio of opposite side and hypotenuse in right angled triangle then triangle with one of the angle greater than 90 can not be a right angled triangle. I know we create right angle triangle with radius as hypotenuse and use it for sin calculation but I never understood that. We actually do not calculate sin of angle greater than 90 degrees. why don't we call this something and why do we relate this with trigonometry. I am sure there is nothing wrong and I did not understand it but i am confused. Please help me.