VB6・VBAメモ：逆正接(アークタンジェント) | フィロの村note

'機能：逆正接関数 '引数：Number：正接(Tan) '戻値：ラジアン Function Atn2(X As Double, Y As Double) As Double If X = 0 And Y = 0 Then Atn2 = 0 ElseIf X > 0 And Y = 0 Then 'θ=0 Atn2 = ((PI / 2) * 0) ElseIf X = 0 And Y > 0 Then 'θ=90 Atn2 = ((PI / 2) * 1) ElseIf X < 0 And Y = 0 Then 'θ=180 Atn2 = ((PI / 2) * 2) ElseIf X = 0 And Y < 0 Then 'θ=270 Atn2 = ((PI / 2) * 3) ElseIf X > 0 And Y > 0 Then ' 0<θ<90 Atn2 = Atn(Abs(Y)