The easiest way is to calculate X and Y parametrically. I used the angle
theta, which I varied from 0 to 360 degrees. I can use cos(theta) and
sin(theta) to get the coordinates of a circle of radius 1. If my ellipse
formula is
(x/a)^2 + (y/b)^2 = 1
then my points are simply related to the above by factors of a and b.
So put angles in column A (0 to 360 in increments of 15 worked adequately
well in my example: this filled A3:A27). Put the values for a and b into
cells B1 and C1. Use this formula in B3 for X:
=B$1*COS(A3*PI()/180)
and use this formula in C3 for Y:
=C$1*SIN(A3*PI()/180)
Fill these formulas down to row 27. Select B3:C27 and create an XY chart
with connecting lines. Then adjust the height, width, and axis scales of the
chart so the grid is square
(
http://peltiertech.com/Excel/Charts/SquareGrid.html), and you'll see your
ellipse.
- Jon
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Jon Peltier, Microsoft Excel MVP
Peltier Technical Services - Tutorials and Custom Solutions -
http://PeltierTech.com/
2006 Excel User Conference, 19-21 April, Atlantic City, NJ
http://peltiertech.com/Excel/ExcelUserConf06.html
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