Question

Sin x= - sin x i didnt understand in case of 2nd quadrant

Answer 1

In Second quadrant Sine is positive...Actually by the angles only Sin is negative in 3rd and 4th quadrants only not in 2nd quadrant.....
Suppose Sin(90-x)=Sinx/because it is in first quadrant
               Sin(90+x)=Sinx/because it's angle is shifted from 0 to 90
               Sin(270+x)=-sinx/It's angle shifted from 0 to 270 and it is in 3rd quadrant