# Add 2 trigonometric functions, with conditions

3 views (last 30 days)
Panagiotis Arvanitis on 22 Sep 2022
Greeting to all,
I am trying to add graphically 2 trigonometric functions:
1. f(x)=a*sin(k*x), graphicaly displayed only for positive value (≥0)
2. g(x)=b*cos(m*x+d), graphicaly displayed only for negative value (≤0)
Thanks

Sam Chak on 22 Sep 2022
Edited: Sam Chak on 26 Sep 2022
Are you trying to plot the addition of two sinusoidal functions, even when there are discontinuities?
x = linspace(-1, 1, 2001);
a = 1;
b = 1;
k = pi;
m = pi;
d = 0;
f = sin(k*x);
g = cos(m*x + d);
fp = f.*(f > 0);
gn = g.*(g < 0);
% Plot
subplot(221)
plot(x, f), grid on, ylim([-1.5 1.5]), title({'\$f(x)\$'}, 'interpreter', 'latex')
subplot(223)
plot(x, g), grid on, ylim([-1.5 1.5]), title({'\$g(x)\$'}, 'interpreter', 'latex')
xlabel({'\$x\$'}, 'interpreter', 'latex')
subplot(222)
plot(x, fp, x, gn), grid on, ylim([-1.5 1.5]), title({'\$f^{+}(x)\$ and \$g^{-}(x)\$'}, 'interpreter', 'latex')
legend({'\$f^{+}(x)\$', '\$g^{-}(x)\$'}, 'interpreter', 'latex', 'location', 'northwest')
subplot(224)
plot(x, fp + gn), grid on, ylim([-1.5 1.5]), title({'\$f^{+}(x) + g^{-}(x)\$'}, 'interpreter', 'latex')
xlabel({'\$x\$'}, 'interpreter', 'latex')

Panagiotis Arvanitis on 26 Sep 2022
Thank you Sam Chak,
Yes, I am trying to add two functions with discontinuities.
I didn't get the same output graph, both positive and negative values appeared.
x = linspace(-0.5, 4, 2001);
a = 1;
b = 1;
k = pi;
m = pi;
d = 0.25;
f = sin(k*x);
g = cos(m*x + d);
% Plot
plot(x, f, x, g, x, f+g), grid on, ylim([-2 2])
xlabel({'\$x\$'}, 'Interpreter', 'LaTeX'),
ylabel({'\$y\$'}, 'Interpreter', 'LaTeX'),
legend({'\$x\$'}, 'Interpreter', 'LaTeX', 'FontSize', 14, 'Location', 'Northwest')
Sam Chak on 26 Sep 2022
I have fixed the code in my Answer.
Please check if that that is the signal desired.

Panagiotis Arvanitis on 26 Sep 2022
I appriciate your hepl!!. It works
Thank you

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