## Wrong answer for sine function

### Ellen Brown (view profile)

on 17 Nov 2019 at 20:09
Latest activity Commented on by Star Strider

### Star Strider (view profile)

on 17 Nov 2019 at 21:01

### Star Strider (view profile)

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

### Star Strider (view profile)

on 17 Nov 2019 at 20:16
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

### Ellen Brown (view profile)

on 17 Nov 2019 at 20:18
I want F in respect to days, how would I do this?

### Star Strider (view profile)

on 17 Nov 2019 at 20:24

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

### Ellen Brown (view profile)

on 17 Nov 2019 at 20:56
thank you!
Star Strider

### Star Strider (view profile)

on 17 Nov 2019 at 21:01
As always, my pleasure!