Viewing in Doors & Windows. Many people use a screwdriver to remove a hinge pin when taking off a door. They simply place the tip up under the head of the pin and then tap on the end with a hammer.
Complementary angles are two angles whose measures add up to 90 degrees. You can think of them as two puzzle pieces that form one 90 degree angle when they are put together. When talking about complementary angles, it's important to remember that they're always in a pair.
Vertical Angles. Vertical angles can be defined as the pairs of non-adjacent angles in opposite positions formed by the intersection of two straight lines are known as vertical angles. In the figure, $\angle$1 and $\angle$3 are a pair of vertical angles. Another pair of vertical angles is $\angle$2 and $\angle$4.