A quarter circular arc can be created easily in keynote.
How to create a quarter circular arc
Select Shape and Circle in the toolbar.
A circle is created.
To improve the visibility, select 「No Fill」 and 「Line」 in Fill tab.
Right click the circle and select 「Make Editable」.
The vertexes becomes editable.
Click the lower left vertex, and delete by pressing the delete key.
The shape changes.
Double click the upper left vertex and the lower right vertex.
The shape becomes a half circle.
Click the midpoint between the upper left vertex and the lower right vertex.
The midpoint is created.
Click the midpoint between the upper left vertex and the upper right vertex.
The midpoint is created.
Click and delete the lower right vertex.
The shape changes.
Double click the lower vertex and the right vertex.
The shape becomes a quarter circle.
Right click the left vertex and select 「Divide Path」.
Right click the right vertex and select 「Divide Path」.
Press the escape key.
Editing is ended.
Right click the shape and select 「Break Apart」.
The shape is divided into an arc and a triangle.
Select the triangle, and delete it.
An quarter circular arc is completed.
