# How to make a line in Mohrcircle

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jeongyeon kim on 20 Dec 2023
Edited: lazymatlab on 20 Dec 2023
I make a Mohrcirlce matlab program and I want to draw line like this. Then how to change the matlab?
% MohrCircle_Area_ex1.m
% This matlab code for Mohr's Aera Circle about cross section
% of the beam.
clear clc clf
format compact
I_x = 3
I_y = 0
I_xy = 2
% R:Radius of a Circle ==================
R = sqrt((I_x- I_y)^2/4+I_xy^2);
% Center of the Mohr's Area Circle ====
I_xc =(I_x+ I_y)/2
I_yc = 0
Theta = atand(I_xy/(I_x-I_xc))/2
% Principal stresses ====================
I_1 = I_xc + R
I_2 = I_xc - R
% Max Value of I_xy : I_max =============
I_max = R
%===== Making Mohr's Circle =============
x=-pi:pi/180:pi;
x1 = R*cos(x)+I_xc;
y1 = R*sin(x)+I_yc;
plot(x1,y1)
title('Make a Mohr Area Circle with R')
xlabel('Normal I')
ylabel('Ixy')
grid on
axis ([I_xc-R, I_xc+R, -2-R, 2+R])
axis equal, hold on
% =========================================
plot([0 0], [-2-R, 2+R]) % y-축
plot([I_xc-2*R I_xc+2*R], [0 0]) % x-축
%==========================================
KSSV on 20 Dec 2023
Pick the points and use plot or line.
jeongyeon kim on 20 Dec 2023
Can you make that commender?

lazymatlab on 20 Dec 2023
Edited: lazymatlab on 20 Dec 2023
Because the center is fixed and the lines would pass the center (because it's Mohr's circle), all you need is either x value of two intersections of line and circle. Then the coordinate of other side of the line is determined.
x1 = 1.799;
y1 = sqrt(R^2 - (x1 - I_xc)^2);
x2 = I_xc - (x1 - I_xc);
y2 = -y1;
plot([x1, x2], [y1, y2], 'm')

RAJA KUMAR on 20 Dec 2023
1. Use the equation of straight line (x-x0)/(x1-x0) = (y-y0)/(y1-y0).
2. Now Decide a variable to store the data for this straight line.
3. Make sure the data you store for x,y are within the limits for the plot you want to show