TITLE: Multiply out the argument of a sine function
QUESTION [0 upvotes]: How do I multiply out the following?
$$y=3.11 \sin (2\pi/365(x-80.75))+12.19$$

I believe the equality should multiply out to
$$y=3.11 \sin(2\pi/365x-323\pi/730)+12.19\,,$$
but I am unsure how to get $-323\pi/730$ inside the sine.

REPLY [2 votes]: Your belief is well-founded: 
$$\frac{2\pi}{365}80.75\left(\frac{2}{2}\right)  = \frac{323\pi}{730}$$
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