In the figure below, $AB$ and $CD$ are parallel. Compute all the angles in the figure.

In the figure below, a parallelogram is divided into four triangles by the diagonals. Calculate the angles of all these triangles.

In the figure below, $AB$ and $DE$ are parallel. Compute the angles of both triangles.

In the figure below, $PQ$ and $RS$ are parallel. Calculate all other angles in the figure.

In the figure below, $AB$ and $CD$ are parallel. Compute the third angle.

In the figure below, $PR$ and $ST$ are parallel. Is there any relation among the angles of the two triangles?

In the figure below, $AB$ and $CD$ are parallel. What is the relation between the angles of the small and large triangles?

Draw a line $AB$ and a line $CD$ parallel to it. Draw a line $EF$ cutting across these lines at the points $M$ and $N$. Measure and write down one of the angles so made. Calculate the other angles. Write down the pairs of corresponding angles, alternate angles, co-interior angles and co-exterior angles.