Originally Posted by

**acc100jt** I didn't say that Sine Rule is wrong.

The triangle I used above is just an example, I should have a triangle which is not isosceles.

My question is that if angle A is obtuse, then we will have to be careful if we find angle A by Sine rule, because the calculator will give the angle in the first quadrant. However, Cosine rule will not. Isn't that a disadvantage of using Sine Rule??

I understand that we may draw diagram to see whether the angle is acute or obtuse, but what if Angle A is an angle between 90 and 100 degrees, that will be difficult to visualise, right? Unless you have super eyesight.