Using ruler and compass only, draw a right angle.
Answer:
Draw a ray OA. With O as the center and any convenient radius, draw an arc, cutting OA at P. With P as the center and the same radius, draw an arc, cutting the arc drawn in step 2 at Q. With Q as the center and the same radius, draw an arc, cutting the arc drawn in step 2 at R. With Q as the center and the same radius, draw an arc. With R as the center and the same radius, draw an arc, cutting the arc drawn in the previous step at B. Draw OB and produce it to C.∠AOC is the angle of measure 90∘.