Start by drawing a segment from P to any of the vertices. Use this segment to construct a 70^(∘) angle.
Practice makes perfect
We are given a triangle with vertices A, B, and C, and a point of rotation P.
We want to draw r_((70^(∘),P))(△ABC). This means that
we want to rotate △ABC by 70^(∘) about point P. To do so, we will follow four steps.
Draw PC and construct a 70^(∘) angle with vertex P and side PC.
Construct PC' such that PC' lies on a side of the angle drawn in the previous step and PC'≅ PC.
Locate A' and B' in a similar manner.
Connect A', B', and C' to draw △A'B'C'.
Let's do it!
Step 1
Let's draw PC.
We will use a protractor to construct a 70^(∘) angle with vertex P and side PC. We start by placing the center of the protractor on P, making sure that the flat part is on PC.
Notice that the inner measuring scale has 0^(∘) on PC. Therefore, we will use the inner measuring scale. Moreover, recall that if it is not 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 A or point B instead of C. We arbitrarily chose point C for simplicity.
Step 2
We will now locate C', which is the image of C 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 C.
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 C'.
Step 3
We can repeat Step 1 and 2 to find A'.
Then we can repeat the same steps to locate B'.
Step 4
Finally, to draw △A'B'C' — which is the image of △ABC after a rotation of 70^(∘) about P — we will connect the obtained vertices.
