How to evaluate a spreadsheet formula within a custom function?

I got this working. Using set value will do the trick. Thus something like this:

function MyFun1(){
  SpreadsheetApp.getActiveSpreadsheet().getActiveSheet().getRange('A1').setValue(Myfun2())
}

function MyFun2(){
   return "=SIN(45)+123"
}

Hope this helps!

Spreadsheet functions from Apps-Script

Not possible - This has been asked many times. Suggest you check the google-apps-script issue list to see if anything has changed. But last I checked, there is no way to do it, and they have no plan to add it. https://code.google.com/p/google-apps-script-issues/issues/list

Ethercalc - java script spreadsheet formulas

If you need to, you can always copy the code from "ethercalc" as it has a java script versions of the spreadsheet formulas. https://github.com/audreyt/ethercalc

I know this is an old question, but it might help someone. just assign the formula to a range, then grab the value.

//asign a formula to the range
var range = sheet.getRange("A1").setFormula("=SUM(D1:D100)");
//get the result
var result  = range.getValue();
//clean up
range.setFormula("");     

I think you need to divide this issue up into two different concerns.

Do you want to grab data that is already on the spreadsheet, perform a calculation, and then print a result, or do you want to use the sin() function on calculations in code unrelated to the data in the spreadsheet?

If you are trying to do the latter, you should be able to reference spreadsheet functions by using Math.sin() in your Google Apps Script. For more information on using the sin() function in JavaScript, check this post out: http://www.w3schools.com/jsref/jsref_sin.asp

If you are trying to do the former, then what you should do is use a readRows() function (more information available here: http://gassnippets.blogspot.com/2012/11/create-your-first-google-apps-script.html) to load your spreadsheet data into a variable (or variables) in memory, perform your calculations, and print the final result out to the spreadsheet using a similar function.

Let me know if this helps.