Lines and Angles - Bisecting

Now, we are going to look at another topic under lines and angles, bisecting. The meaning of this can be derived from the name itself. 'Bi' means 2 and bisecting means dividing something exactly in half, like this orange here,

But In this lesson. we will only look at line and angle bisecting. 

You might think that we could bisect a line just by marking the midpoint and drawing a line through it. But this is not quite so simple. If you draw a line like that, It might not be straight or exactly perpendicular to the original line. So it can't be taken as a bisector. 

To correctly bisect a line, we need a compass. We open the compass wider than half of the given line and place it one one end of the line. Then we draw an arc on both sides of the line. We do the same thing after placing compass on the other end of the line. Now we have to arcs on either side of the line. It will appear like this,


Then we just have to plot points at the intersecting points of the arcs and join them. Then we get a perfect bisector of the line.


Now lets look at how to bisect angles. To divide an angle by 2, we also use a compass but the steps are completely different. For example, lets look at this angles,


to bisect it, we first open the compass narrower than half of the side lines on the angle and place it at the vertex,

Vertex is marked in red in the above example. After placing the compass here, we have to draw an arc on each of the side lines. 

After that, we put the compass on the intersecting point of arc and side line, the ones marked in red above, and draw an arc in the middle. 

Then we mark the intersecting point of these 2 arcs and draw a line connecting it and the vertex. 


And now we have successfully bisected this angle! Simple right? If you still feel the need for deeper understanding, watch the video below. 

Lines and Angles (2).mp4 

This lesson would not be complete if you didn't try this on your own would it? So remember to finish the worksheet and quiz given below.

Worksheet:
Lines and Angles - Bisecting.pdf 

Quiz:
https://kahoot.it/challenge/05878656?challenge-id=fce05bca-e50a-4334-bddd-75cf60734864_1713994300008

Or go to Kahoot and use the code 05878656 







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