__maths__>__Construction / Practical Geometry (basics)__>__Standard angles Using Campus__### constructing `90^@` using a compass

In this page, a short and to-the-point overview of constructing `90^@` angle using a compass is provided.

*click on the content to continue..*

Which of the following help to construct `90^@` angle using a compass?

- construct two `60^@` and bisect the second `60^@`
- construct two `60^@` and bisect the second `60^@`
- `90^@` angle cannot be constructed using a compass

The answer is "construct two `60^@` and bisect the second `60^@`"

Constructing `90^@` with two `60^@` is illustrated

• With an arbitrary distance-measure on compass, mark point `P` from point `A` on line `bar(AB)`.

• With the same distance measure on compass, construct two arcs from points `A` and `P`. The arcs cut at point `Q`. `bar(AQ)` makes `60^@` with the `bar(AP)`.

• With the same distance measure on compass, construct two arcs from points `A` and `Q`. The arcs cut at point `R`. `bar(AR)` makes `120^@` with the `bar(AP)`.

• With an arbitrary distance-measure on compass, construct two arcs from points `Q` and `R`. These arcs cut at point `S`. The line `bar(AS)` bisects the angle `/_QAR`.

The angle `90^@` is constructed as `/_PAS`.

**Constructing `90^@` angle using a compass** : Construct two equilateral triangles and bisect the second one to construct `90^@` angle.

*slide-show version coming soon*