Brainlag Plus
Brainlag PlusConstructions on a grid
The ruler-and-compass constructions, checked the way a mark scheme checks them: by where the constructed line or point must be.
What each construction gives
- Perpendicular bisector of AB: every point on it is the same distance from A and from B. It passes through the midpoint of AB at right angles.
- Angle bisector: every point on it is the same distance from the two arms of the angle.
- Perpendicular from a point to a line: the shortest distance from the point to the line.
- Triangle from three sides: arcs of the two other lengths from the ends of the base cross at the third corner.
On a paper, leave the arcs showing: they earn the method marks. A mark scheme then checks the result with a ruler, within about 2 mm.
The rest of this lesson and its 11 practice questions are in Plus.
Screen 1 of 3, free to read.
- 11 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards