This is one of the easiest topics to score in PMR Math exam especially if your languages are good. Even if you are not, you can observe how the sentences look like and eventually you will remember them too. This topic has been appearing in both paper 1 and paper 2 so far. And what do you need to know to master this Form 2 chapter 9 topic? There are basically three important points to note.

First of all, do you know how many loci there are altogether? Yes? That is good for you. You are one third there. No? My question to you is, “As in a game of DotA, if you do not know your team players or assuming you do not know where the opponents’ Ancients are, then how are you going to destroy them?” You have to know your team players well to form strategies and to work closely together to destroy the opponents’ Ancients in order to win the game. It is the same for Math. If you do not know how many loci there are altogether? Then how could master the chapter?

Some of you might have already flipped through your textbook and found out that there are a total of four loci in the chapter of Loci in Two Dimensions namely, Circle, Perpendicular bisector, Parallel line and Angle bisector. The second point you must know is how each locus is defined. For example, the locus of a circle is usually describe as a locus with constant distant from a fixed point. In some questions, instead of using the words constant distant, the question may say directly, “locus of X is 4 units from the point P or some questions may be in this format where it tell you that the locus of Y such that YJ is equaled to JN (refer to the picture on the right).

Therefore, it is important to know how each type of locus is defined and the variations of the definition. Perpendicular bisector is usually defined as a locus that is equidistant from two fixed points or the question may say directly ‘equidistant from P and Q.‘ For Parallel line, it is defined as constant distant from a line or question may tell you directly that the locus is 1 cm or constant distant from AB. The last of the locus is Angle bisector which is defined as a locus equidistant from two lines or directly (looking at the previous picture on the right)equidistant from SR and SP.

You may ask me, “How can I know the variations of the definition of each type of locus?” My answer will be pretty straight forward – Practice.” Through practicing, not only will you gain confidence in tackling questions on Loci, you will also learn the variations of the definition of each type of locus.

Before ending this post, the third point to mastering Loci in Two Dimensions is to know how to draw each type of Locus.

What you need to know for the last part of the question is usually the intersection of two loci; the intersection point/points will satisfy the conditions of the two loci.

So you can see that Loci in Two Dimensions is an easy topic which you can score. All you need to know are:

1. How many different type of locus in this chapters and the name for each locus.
2. The definition for each type of locus.
3. How to draw each type of locus.

After knowing this, the key to mastering this topic is still – Practice!