G-CO.12 Construction #2. Copying an Angle.
Given angle ABC, copy the angle using only a compass and straightedge.
Steps.
1. Draw ray DE. (Do this away from the figure.)
2. Draw point F on ray BC between B and C.
3. Use a compass to draw an arc centered at B that intersects rays BA and BC at points F and G.
4. Draw an arc with the same compass measurement as step 3, but centered on D that intersects ray DE at H.
5. Use a compass to measure an arc (and draw the arc) centered at G that goes through F.
6. Use a compass to draw an arc with the same measurement as step 4, centered at H, intersecting the arc from step 3 at point I.
7. Draw ray DI.