Angles with set squares
Draw BC = 5.5 cm and construct ∠ABC = 30° at B with set squares.
Draw BC = 5 cm and construct ∠ABC = 45° at B with set squares.
Draw BC = 5 cm and construct ∠ABC = 60° at B with set squares.
Draw BC = 5 cm and construct ∠ABC = 90° at B with set squares.
Draw BC = 5 cm and construct ∠ABC = 120° at B with set squares.
Draw BC = 5 cm and construct ∠ABC = 135° at B with set squares.
Draw BC = 5 cm and construct ∠ABC = 150° at B with set squares.
1. Draw BC = 5.5 cm.
2. Put the 30° corner of the 30°/60° set square on B, with one edge along BC.
3. Draw a line from B along the other edge, and mark A on it.
4. Take the set square away: ∠ABC = 30°.
1. Draw BC = 5 cm.
2. Put a 45° corner of the 45° set square on B, with one edge along BC.
3. Draw a line from B along the other edge, and mark A on it.
4. Take the set square away: ∠ABC = 45°.
1. Draw BC = 5 cm.
2. Put the 60° corner of the 30°/60° set square on B, with one edge along BC.
3. Draw a line from B along the other edge, and mark A on it.
4. Take the set square away: ∠ABC = 60°.
1. Draw BC = 5 cm.
2. Put the right-angled corner of the 30°/60° set square on B, with one edge along BC.
3. Draw a line from B along the other edge, and mark A on it.
4. Take the set square away: ∠ABC = 90°.
1. Draw BC = 5 cm.
2. Put the right-angled corner of a set square on B, with one edge along BC.
3. Hold it still, and put the 30° corner of the 30°/60° set square on B too, against its upright edge.
4. Draw a line from B along the outer edge of the second set square, and mark A on it.
5. Take the set squares away: ∠ABC = 90° + 30° = 120°.
1. Draw BC = 5 cm.
2. Put the right-angled corner of a set square on B, with one edge along BC.
3. Hold it still, and put a 45° corner of the 45° set square on B too, against its upright edge.
4. Draw a line from B along the outer edge of the second set square, and mark A on it.
5. Take the set squares away: ∠ABC = 90° + 45° = 135°.
1. Draw BC = 5 cm.
2. Put the right-angled corner of a set square on B, with one edge along BC.
3. Hold it still, and put the 60° corner of the 30°/60° set square on B too, against its upright edge.
4. Draw a line from B along the outer edge of the second set square, and mark A on it.
5. Take the set squares away: ∠ABC = 90° + 60° = 150°.
Why it works
The corners of the set squares are made to exact angles: 30°, 60° and 90° on one, 45°, 45° and 90° on the other. A corner placed on B with one edge along BC gives its own angle; two corners side by side, sharing an edge, add up.