Hello Jerry,
Thanks for your promt reply.
I agree with you. But in the formula shown, the end result is given in
Degrees which is what I want. In first exemple the included angle happens to
be less than 90 degrees.
In the second exemple the result for the included angle is grater than 90
degrees.

"Jerry W. Lewis" wrote:

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