Excel's trig functions work in radians, not degrees. See Help for the
DEGREES() and RADIANS() functions.

Jerry

"Serge" wrote:

A51=25.0
B51=21.5407
C51=42.03 Degrees
In E51
=IF(OR(A51="",B51="",C51=""),0,DEGREES(ATAN(A51*SI N(RADIANS(C51))/(B51-A51*COS(RADIANS(C51))))))
The answer is 79.935 Degrees
The formula above works well because the result is less than 90 Degrees
But in the next scenario:
A51=76.673
B51=47.214
C51=9.50 Degrees
I get -24.01 Degrees The answer should be 155.99 Degrees.

Can someone help with this one.
Many Thanks in advance.
Serge