Finding the x interval for when a function is less than another

I plotted two functions 'phi' and 'RHS' and I am trying to figure out how to find the x intervals for when 'phi' is less than or equal to 'RHS'. Is there a simple code that would directly give me the x intervals and possibly highlight them on the plot.

clear all;

clc;

x=-1:0.01:5;

y=x.*(x-2).*(x-4).^2;

dy=4*x.^3-30*x.^2+64*x-32;

a=0:0.01:5;

phi= a.^4 - 10.*a.^3 +32.*a.^2 -38.*a+15;

dphi=4.*a.^3 -30.*a.^2 +64.*a -38;

c1=0.01;

figure(1)

plot(x,y)

RHS= 15 - c1.*a.*38;

figure(2)

plot(a,phi,a,RHS)

Answer 1

[Jordy Jose]

Hello,

To find the intervals of x where 'phi' is less than or equal to 'RHS', you may use "find" function. For example:

 >>inds = find(phi <= RHS);
 >>a(inds)