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TAN and ATAN functions ...
(a) From a formula: Y = TAN (X)
(b) if X=2.0 (in Radian) that's equivalent to 115 degrees (c) Then = Y = tan (2) = tan (115 degrees) = -2.18 (d) Now I can reverse the formula to X = ATAN (Y) (e) But, X=ATAN (-2.18) = -1.14; NOT 2.0 that I expected it to return -- see statement (b) Why is it so? Thanks |
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TAN and ATAN functions ...
"OTS" wrote in message
... (a) From a formula: Y = TAN (X) (b) if X=2.0 (in Radian) that's equivalent to 115 degrees (c) Then = Y = tan (2) = tan (115 degrees) = -2.18 (d) Now I can reverse the formula to X = ATAN (Y) (e) But, X=ATAN (-2.18) = -1.14; NOT 2.0 that I expected it to return -- see statement (b) Why is it so? From the help: ATAN returns a value in the range -pi/2 to +pi/2. You need to remind yourself that all the trig functions will wrap round at 180 degree intervals. -- David Biddulph |
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