At 17:56 03/03/2016 +1100, Keith Bainbridge wrote (privately):
On 28 February 2016 at 16:48, Brian Barker wrote:
At 19:19 27/02/2016 +1100, Keith Bainbridge wrote:
I'm trying to draw a diamond shape with 2 opposing angles equal,
one angle 72 degrees and its opposite 60 degrees. I figured I
should be able to stretch a standard supplied shape, but can't
figure how to hold the plane of the equal angles so that the
distances from the points will vary. Then how to know that I have
72 degrees. Any pointers please?
The internal angles of any quadrilateral must add up to 360
degrees. You appear to have two lots of 72 degrees and two of 60
degrees - leaving you 96 degrees short. Color me more confused.
Sorry for the confusion.
The internal angles as I walk around the rhombus will be 72, 114,
60, 114 degrees.
That won't be a rhombus, then - which needs to be equilateral - but a kite.
Here's an idea:
The shape you want is two isosceles triangles joined at their bases.
The 72-degree end has other internal angles of 54 degrees. The
60-degree end is an equilateral triangle (which is a special case of
isosceles, of course).
o Click the drop-down (-up?) menu next to the Basic Shapes icon in
the Drawing toolbar and then Isosceles Triangle.
o Drag to create a triangle.
o Using Position and Size..., set the width to some suitable value, say 100 mm.
o Applying the sine rule to the 72-degree triangle, its height needs
to be 50 x sin(54 deg.) / sin (36 deg.) so set the height to 68.82 mm.
o Repeat the process to create a second isosceles triangle.
o Using Position and Size..., set rotation angle to 180 degrees, so
as to invert it.
o Using Position and Size..., set the width to the same 100 mm as before.
o Applying Pythagoras's Theorem to this equilateral triangle, its
height needs to be 50 x sqrt(3) mm, so set the height to 86.60 mm.
o Now move the two triangles together. You can move them using the
arrow keys and Alt+arrow for finer control, Probably more sensibly,
you can set the Y-positions of both shapes to be the same, whilst
choosing different base points (one top, the other bottom) for the two.
o Click one shape and Alt+click the other, so that the combination is selected.
o Go to right-click | Group to combine the two shapes into one.
o Use right-click | Line... to set the line style to none, to remove
the tell-tale common boundary.
You can easily move, rescale, and rotate the shape as required, of course.
I trust this helps.
Brian Barker
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@openoffice.apache.org
For additional commands, e-mail: users-h...@openoffice.apache.org
