This construction takes one given angle and copies it adjacent to another, creating a larger angle whose measure is the sum of the two.
By carrying out this construction more than once, any number of angles can be summed. This can be done by adding each successive angle to the left or the right of the accumulating angle.
In a similar way, angles can be 'subtracted'. See the construction: Difference of two angles.
The above animation is available as a printable step-by-step instruction sheet, which can be used for making handouts or when a computer is not available.
|1||Angle ∠BAC is congruent to angle ∠SPR||Copied using the procedure described in Copying an angle. See that page for proof.|
|2||m∠SPQ = m∠SPR + m∠RPQ||Adjacent angles.|
|3||m∠SPQ = m∠BAC + m∠RPQ||From (1), (2)|