Relative position of 2 points on a circle 2

[ziggyS]

hi
this question was addressed in thread770-356581 but the resulting formula is only valid for points within 90 degrees of each other

stevenal (Electrical) 21 Jan 14 20:12
'=DEGREES(ASIN(SIN(RADIANS(A1-A2))))'
Excel

recap if point A1 is at position 358 degrees
point A2 is at position 01 degrees
above formula returns -3 (position of A1 relative to A2)

but if point A1 is at position 180 degrees
point A2 is at position 01 degree
above formula returns +1 (required return is +179)

can anyone expand on above formula to be valid over complete circle (+- 180)

thanks
ziggyS

 

[ziggyS]

i have changed formula to
'=DEGREES(ACOS(COS(RADIANS(A1-A2))))'
which returns the correct whole number but i lose the polarity

 

[IDS]

This should work (it works for your examples):

=DEGREES(ATAN2(COS(RADIANS(A1-A2)),SIN(RADIANS(A1-A2))))

There may be a simpler way, but I doubt it can be done with just sin or just cos.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[ziggyS]

thanks IDS absolutely perfect!