Start by drawing a segment from P to any of the vertices. Use this segment to construct a 90^(∘) angle.
Practice makes perfect
We are given a rectangle with vertices R, E, C, and T, and a point of rotation P.
We want to rotate RECT by 90^(∘) about point P. To do so, we will follow four steps.
Draw PR and construct a 90^(∘) angle with vertex P and side PR.
Construct PR' such that PR' lies on a side of the angle drawn in the previous step and PR'≅ PR.
Locate E', C' and T' in a similar manner.
Connect E', C', T', and R' to draw R'E'C'T'.
Let's do it!
Step 1
Let's draw PR.
We will use a protractor to construct a 90^(∘) angle with vertex P and side PR. We start by placing the center of the protractor on P, making sure that the flat part is on PR.
Notice that the inner measuring scale has 0^(∘) on PR. Therefore, we will use the inner measuring scale. Moreover, recall that unless otherwise specified, we measure the angle in the counterclockwise direction.
Finally, to construct the angle, we remove the protractor and draw a ray from P that passes through the mark we have just drawn.
Note that for this step we could have chosen point E, C, or point T instead of R. We arbitrarily chose point R for simplicity.
Step 2
We will now locate R', which is the image of R after the rotation. To do so we will use a compass. We will start by placing the sharp spike of the compass at P and the leg with the pencil at R.
Without modifying the amplitude of the compass, we will keep the sharp spike at P. Then we will draw an arc intersecting the ray we drew in the previous step. This point of intersection is R'.
Step 3
We can repeat Steps 1 and 2 to find E'.
Then we can repeat the same steps to locate C'.
Let's repeat the same steps to locate T'.
Step 4
Finally, to draw R'E'C'T' — which is the image of RECT after a rotation of 90^(∘) about P — we will connect the obtained vertices.
