When two lines intersect each other at a point, the vertically opposite angles are equal.All angles of vertically opposite angles add upto 180°. A straight line crosses two parallel lines:Corresponding angles are equal – we look for an F shape which may be upside down and/or back to front.
Let A lie between B and C on the line BC, and also between D and E on the line DE. Then BAD and CAE are called vertically opposite
angles.vertically opposite angles are normally equal in measure.
The idea is to add the same supplementary angles to both, getting 180.
|BAD| + |BAE|
|CAE| + |BAE| = 180;
so subtracting gives:
|BAD| - |CAE| = 0 ;
|BAD| = |CAE|
General properties of Angles:
From the given vertically opposite angle shown below, Find angles a°, b° and c° ,
Because b° is vertically opposite 60°, it must also be 60°
A full circle is 360°, so that leaves 360° - 2×60° = 240°
Angles a° and c° are also vertically opposite, so must also be equal, which means they are 120° each.
Answer: a = 120°, b = 60° and c = 120°.