The trigonometric function sine, like the cosine and the tangent, is based on a rightangled triangle. In mathematics, you can find the sine of an angle by dividing the length of the side opposite the angle by the length of the hypotenuse. You can save time and frustration by using Excel functions to make this calculation.
These instructions apply to Excel 2019, 2016, 2013, 2010, Excel Online, and Excel for Microsoft 365.
Working With Degrees vs. Radians
Using the SIN function to find the sine of an angle might be more convenient than doing it manually, but first, you need to express the angle in radians rather than degrees.
As it happens, you can use Excel's RADIANS function to convert an angle from degrees to radians as shown in cell B2 in the image above where the angle of 30degrees is displayed as 0.523598776 radians.
Another option to convert degrees into radians is by using Excel's PI function in the formula as shown in row 4 in the example image.
SIN Function Syntax and Arguments
A function's syntax refers to the layout of the function and includes the function's name, brackets, and arguments.
The syntax for the SIN function is as follows:
The number is the angle's measurement in radians. For this argument, you can input the data directly or input the cell reference to the location of this data in the worksheet.
Using Excel's SIN Function
This example covers the steps needed to enter the SIN function into cell C2 to find the sine of a 30degree angle or 0.523598776 radians.
Options for entering the SIN function include manually typing in the entire function =SIN(B2), or using the Function Dialog Box, as outlined below.

Click on cell C2 in the worksheet to make it the active cell.

Click on the Formulas tab of the ribbon menu.

Choose Math & Trig from the ribbon to open the function dropdown.

Click on SIN in the list to bring up the Function Dialog Box.

Click on the Number line.

Click on cell B2 in the worksheet to enter that cell reference.

Click Done to complete the formula.

The answer 0.5 will appear in cell C2, which is the sine of a 30degree angle.
#VALUE! Errors and Blank Cell Results
The SIN function displays the #VALUE! error if the reference used as the function's argument points to a cell containing text data.
If the cell reference points to an empty cell, the function returns a value of zero. Excel's trig functions interpret blank cells as zero, and the sine of zero radians is equal to zero.