Draw 90 deegre angle

Constructing a 90º Angle

We can construct a 90º angle either by bisecting a straight angle or using the following steps.

Step 1:  Draw the arm <i>PA</i>.
Step 2:  Place the point of the compass at <i>P</i> and draw an arc that cuts the arm at <i>Q</i>.
Step 3:  Place the point of the compass at <i>Q</i> and draw an arc of radius <i>PQ</i> that cuts the arc drawn in Step 2 at <i>R</i>.
Step 4:  With the point of the compass at <i>R</i>, draw an arc of radius <i>PQ</i> to cut the arc drawn in Step 2 at <i>S</i>.
Step 5:  With the point of the compass still at <i>R</i>, draw another arc of radius <i>PQ</i> near <i>T</i> as shown.
Step 6:  With the point of the compass at <i>S</i>, draw an arc of radius <i>PQ</i> to cut the arc drawn in step 5 at <i>T</i>.
Step 7:  Join <i>T</i> to <i>P</i>. The angle <i>APT</i> is 90º.