Why do my Excel "pre-installed" functions not work right?

Question

I want to use SIN(any angle). I know how to use the SIN function, but when I do it I get something like this:

SIN(30) = 0.998...

When really, Sin(30) = 0.5!

Thank you!

Answer 1

You must type =SIN(30*PI()/180) into the cell to get the proper .5 answer.

Answer 2

That's because the SIN function is taking the sign of 30 radians and not 30 degrees.

Use this instead:

=SIN(RADIANS(30))

Then you will get your 0.5 answer.

You can also create a custom function to solve this problem. Go to Tools > Macros then Record New Macro. Then on the window that pops up change "Store Macro In" to "Personal Macro Workbook" then click OK.

Hit the stop button that pops up to stop recording the macro.

Then go to Tools > Macro > Macros

And select your Macro. It should be something like:

PERSONAL.XLS!Macro1

Then click Edit.

Once you click Edit a new window will appear. Select all of of the text in the window and delete it. Then paste in the following text:

Function DegSIN(Num)
DegSIN = ""

DegSIN = Sin(Application. _
WorksheetFunction.Radians(Num))

End Function

Then click the save button in that window and close out the window. Then go back into Excel and type:

=DegSIN(30)

You should get an answer of 0.5.

Congratulations! If you did that you just created your own custom function that returns the SIN of degrees instead of radians.

Since that function is stored in the Personal workbook it will be available each time you use Excel.