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You can easily create and display supplementary angles using `GeoGebra`

.

`GeoGebra`

Instruction 1

- 1.
- Open
`Graphics View`

under`View`

in`Menu`

. - 2.
- Select
`Line`

and draw a line in`Graphics View`

. You should also get two points on your line named $A$ and $B$. - 3.
- Select
`Point on Object`

and draw a point that is between $A$ and $B$. This point will get the name $C$. - 4.
- Select
`Point`

and draw a point outside of the line from the previous step. This point will get the name $D$. - 5.
- Select
`Angle`

and click$A$, $C$ and $D$,

in that order. Repeat for the points

$D$, $C$ and $B$.

- 6.
- Select
`Move`

and drag point $D$ around. You’ll see that the sum of the two angles you drew is always $180$°.

`GeoGebra`

Instruction 2

- 1.
- Open
`Graphics View`

under`View`

in`Menu`

. - 2.
- Select
`Line`

. Click two points in the plane in`Graphics View`

, but be sure to click the leftmost point first. You should get a line with two points named $A$ and $B$, where $A$ is the leftmost point of the two. - 3.
- Select
`Point`

and draw a point above the line from the previous step. This point will be given the name $C$. - 4.
- Select
`Segment`

and click $B$ and $C$. - 5.
- Select
`Parallel line`

and click point $A$, then the line segment you drew in the previous step. - 6.
- Select
`Perpendicular Line`

and click point $C$, then the parallel line you drew in the previous step. - 7.
- Select
`Intersect`

and click the lines from Steps 5 and 6. This point should get the name $D$. - 8.
- Select
`Angle`

and click the points$C$, $B$, and $A$,

in that order. After the angle is drawn, click the points

$B$, $A$, and $D$,

in that order.

- 9.
- Select
`Move`

and drag point $C$ around while making sure it’s always above the line. You’ll see that the sum of the two angles you drew is always $180$°.