Semicircles

Bungee · Apr 23rd, 2002, 07:25 AM

I was wondering if anyone can help me out, I have a number of sets of data comprising two numbers each in the x domain (y=0), I need to plot a semicircle between these two numbers with the flat edge along the x-axis and the arc in the positive y.

Any suggestions, I've been told I can do it and that I need the equation of a semicircle if that's any help?

lenze · Apr 23rd, 2002, 07:51 AM

Use the XY (Scatter) chart format connected with smooth lines. You will need a lot of data points to produce a smooth curve.

Bungee · Apr 23rd, 2002, 07:53 AM

But how do I find those points?

lenze · Apr 23rd, 2002, 08:01 AM

If I remember right from college math, (It's only been 35 years), the formula for a circle graph is x^2 + y^2 =r^2. For a semicircle, omit the negative y values

Tim Francis-Wright · Apr 23rd, 2002, 10:33 AM

Assuming that you want the semicircle to start at the origin and be in the upper-right
quadrant of the plane, with the flat part of the semicircle along the x axis, then your
equation would be:
(x-r)^2+y^2=r^2
or y^2 = 2rx - x^2
or y = (2*r*x - x^2)^.5, for 0<=x<=2r

Apr 23rd, 2002, 10:33 AM	#5
Tim Francis-Wright Board Regular Join Date: Feb 2002 Posts: 74	Assuming that you want the semicircle to start at the origin and be in the upper-right quadrant of the plane, with the flat part of the semicircle along the x axis, then your equation would be: (x-r)^2+y^2=r^2 or y^2 = 2rx - x^2 or y = (2rx - x^2)^.5, for 0<=x<=2r __________________ "Interfere? Of course we should interfere! Always do what you're best at, that's what I say!" -- The Doctor, Nightmare of Eden

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Apr 23rd, 2002, 07:25 AM	#1
Bungee New Member Join Date: Apr 2002 Posts: 2	I was wondering if anyone can help me out, I have a number of sets of data comprising two numbers each in the x domain (y=0), I need to plot a semicircle between these two numbers with the flat edge along the x-axis and the arc in the positive y. Any suggestions, I've been told I can do it and that I need the equation of a semicircle if that's any help?

Apr 23rd, 2002, 07:51 AM	#2
lenze MrExcel MVP Join Date: Feb 2002 Location: Helena, MT Posts: 13,690	Use the XY (Scatter) chart format connected with smooth lines. You will need a lot of data points to produce a smooth curve.

Apr 23rd, 2002, 07:53 AM	#3
Bungee New Member Join Date: Apr 2002 Posts: 2	But how do I find those points?

Apr 23rd, 2002, 08:01 AM	#4
lenze MrExcel MVP Join Date: Feb 2002 Location: Helena, MT Posts: 13,690	If I remember right from college math, (It's only been 35 years), the formula for a circle graph is x^2 + y^2 =r^2. For a semicircle, omit the negative y values