Convert Angles from Degrees to Radians in Excel

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Convert Angles from Degrees to Radians in Excel

Excel has a number of built-in trigonometric functions that make it easy to find:

of a right-angled triangle (a triangle containing an angle equal to 90o). The only problem is that these functions require the angles to be measured in radians rather than degrees, and while radians are a legitimate way of measuring angles - based on the radius of a circle - they are not something most people work with on a regular basis.

To help the average spreadsheet user get around this problem, Excel has the RADIANS function, which makes it easy to convert degrees to radians.

An alternative, as shown in row four in the image above, is to multiply the angle by the PI() function and then divide the result by 180 to get the angle in radians.

Historical Note

Apparently Excel's trig functions use radians rather than degrees because when the program was first created, the trig functions were designed to be compatible with the trig functions in the spreadsheet program Lotus 1-2-3, which also used radians and which dominated the PC spreadsheet software market at the time.

The RADIANS Function's 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 RADIANS function is:

Angle - (required) the angle in degrees to be converted to radians
- the size of the angle in degrees can be entered for this argument - as shown on line 2 in the image above - or the cell reference to the location of this data in the worksheet can be entered instead.

As shown in the image above, this example will use the RADIANS function to convert a 45 degree angle to radians.

The information below covers the steps used to enter the RADIANS function into cell B2 of the worksheet.

Options for entering the function and its arguments include:

2. Selecting the function and its arguments using the RADIANS function dialog box

Although it is possible to just enter the complete function manually, many people find it easier to use the dialog box as it takes care of entering the function's syntax - such as brackets and comma separators between arguments.

Opening the Dialog Box

The steps below detail the steps used to enter the RADIANS function and arguments into cell B7 using the function's dialog box.

1. Click on cell B2 in the worksheet - this is where the function will be located
2. Click on the Formulas tab of the ribbon menu
3. Choose Math & Trig from the ribbon to open the function drop down list
4. Click on RADIANS in the list to bring up the function's dialog box

Entering the Function's Argument

For some Excel functions, such as the RADIANS function, it is an easy matter to enter the actual data to be used for the argument directly into the dialog box - as shown in cell B3.

However, it is usually best to never use actual data for a function's argument - for one, it makes it easier to update the worksheet - this example will enter the cell reference to the data as the function's argument.

1. In the dialog box, click on the Angle line.
2. Click on cell A2 in the worksheet to enter the cell reference as the function's argument
3. Click OK to complete the function and return to the worksheet
4. The answer 0.785398163397448 should appear in cell B2, which is 45 degrees expressed in radians
5. When you click on cell B1 the complete function = RADIANS ( A2 ) appears in the formula bar above the worksheet

Trigonometry and Excel

Trigonometry focuses on the relationships between the sides and the angles of a triangle, and while many of us do not need to use it on a daily basis, trigonometry has applications in a number of fields including astronomy, physics, engineering, and surveying.

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