One of the angles formed at the intersection of two straight lines is equal to 40 degrees.

One of the angles formed at the intersection of two straight lines is equal to 40 degrees. Find the degree measures of acute angles.

When they intersect, the straight lines form two pairs of vertical angles (angles with a common vertex that are opposite each other). Such angles are equal to each other. Obviously, the degree measure of the angle opposite the 40 ° angle is also 40 °.

In this case, intersecting, the straight lines form pairs of adjacent corners (corners with a common side). The sum of the degree measures of such angles is 180 °. Let’s define other unknown angles, which are also vertical and equal to each other:

180 ° – 40 ° = 140 °.