When giving the following basic trigonometry question in F.4 additional mathematics lesson:
Given , prove that .
It should be extremely easy, just write , however, a student gave
Oops, actually, that means the equation above telling us
but, we all know that is undefined, so what’s wrong?
P.S. Patrick, I can’t update my blog too often now, because I’m busy working in a job and my family is moving to a new flat, so I can’t access internet at home recently.