Idea 21of 24Builds onBuild a triangle from three sidesA triangle's angles make 180°Draw an angle with a protractor
Build from a base and two angles
How do you draw a triangle from one side and two angles?
Today you'll discover
- which tool draws the angles
- where the third corner appears
- what the third angle will be
Think firstA 6 cm base, 50° at A and 60° at B
You know the base and the angles at both its ends. Where is corner C?
Decide first, then press Next. Watch the two new arms until they cross.
A 6 cm base from A to B. An arm is drawn from A at 50°, then an arm from B at 60°; they cross at C, which is marked and joined, and the angle at C reads 70°. The last step shows a 5 cm base with a square corner at A and 40° at B.
See the whole ideathe big idea and the key word, in one place
The big idea
Draw the base, draw each end's angle with a protractor, and the arms cross at the third corner.
Easy to get wrongAt B the base runs the other way. Count on the scale whose 0 sits on the base at B.
Two ways to buildKnow three sides: use a compass. Know one side and the two angles at its ends: use a protractor.
Key word
- base
- the side a triangle is drawn on first, usually along the bottom
Ready to use it?
- Construct a triangle from one side and two angles.