Under the O-level additional math syllabus, students are expected to know the values of several trigonometry special angles (Such as Sin30, Cos 45 and Tan 60 etc).
The standard chart given in all textbooks and notes will be as follows:
Method 1: How to remember?
The chart below is an easier version to remember. Simply observe the nice pattern of sin(x) from left to right, and cos(x) from right to left. Lastly, obtain tan(x) using the identity tan(x) = sin(x)/cos(x) .
Method 2: What if you really forget the values during exam?
During the O-level or prelim examinations, when the question states “without the use of a calculator”, it means we have to give the exact value of the trigo special angle. However, we still have access to the calculator. Hence during examination, if you cannot recall the special angle, one way is to evaluate the square of the trigonometric function using the calculator and then add a square root sign to it. The reason we square it is because it will always return a nice, rational number on the calculator.
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