Wrong answer for sine function

I am trying to create a function to evaluate sine at different values of t

function F = rforce(t)
F = 0.3 + 0.2.*sin(2.*pi.*t/365 - pi/2);
end

but this gives the incorrect answer when ran in matlab

[Star Strider]

It would appear that the units of ‘t’ are days, so ‘F’ would be with respect to years (or fractions of years).

What result do you want?

[Ellen Brown]

I want F in respect to days, how would I do this?

Answer 1

[Star Strider]

Define ‘t’ in terms of days (or fractions of days).

Try this:

rforce = @(t) 0.3 + 0.2.*sin(2.*pi.*t/365 - pi/2);

tdays = 1:0.25:365.25;                                  % One Year in 6-Hour Increments

figure
plot(tdays, rforce(tdays))
grid
xlabel('Days')
ylabel('r Force')
xlim([min(tdays) max(tdays)])

[Ellen Brown]

thank you!

[Star Strider]

As always, my pleasure!