The [[TAN]] function returns the ratio of [[SIN]]e to [[COS]]ine or tangent value of an angle measured in radians.


{{PageSyntax}}
::: tangent! = '''TAN('''''radian_angle!''''')'''


{{Parameters}}
* The ''radian_angle'' must be measured in radians. 


{{PageDescription}}
* To convert from degrees to radians, multiply degrees * π/180.
* TANGENT is the gradient or slope of the circle or arc at [[SIN]](θ) / [[COS]](θ). Do not use division when the [[COS]] = 0 to avoid [[ERROR Codes|errors]].


''Example:'' Spiraling text using the [[SIN]] and [[TAN]] functions.
{{CodeStart}} '' ''
{{Cl|DIM}} {{Cl|SHARED}} text {{Cl|AS}} {{Cl|STRING}}
text$ = "S P I R A L"
{{Cl|DIM}} {{Cl|SHARED}} word(1 {{Cl|TO}} {{Cl|LEN}}(text$) * 8, 1 {{Cl|TO}} 16)

{{Cl|CALL}} analyse
{{Cl|CLS}}
{{Cl|CALL}} redraw

{{Cl|SUB}} analyse
{{Cl|CLS}}
{{Cl|SCREEN}} 12
{{Cl|COLOR}} 2: {{Cl|LOCATE}} 1, 1: {{Cl|PRINT}} text$
{{Cl|DIM}} px {{Cl|AS}} {{Cl|INTEGER}}, py {{Cl|AS}} {{Cl|INTEGER}}, cnt {{Cl|AS}} {{Cl|INTEGER}}, ltrcnt {{Cl|AS}} {{Cl|INTEGER}}
px = 1: py = 1
DO
  word(px, py) = {{Cl|POINT}}(px, py)
  {{Cl|PSET}} (px, py), 1
  px = px + 1
  {{Cl|IF...THEN|IF}} px = {{Cl|LEN}}(text$) * 8 {{Cl|THEN}}
    px = 1
    py = py + 1
  {{Cl|END IF}}
{{Cl|LOOP}} {{Cl|UNTIL}} py = 16
{{Cl|END SUB}}

{{Cl|SUB}} redraw
{{Cl|CLS}}
{{Cl|DIM}} row {{Cl|AS}} {{Cl|INTEGER}}, cnt {{Cl|AS}} {{Cl|INTEGER}}, cstart {{Cl|AS}} {{Cl|SINGLE}}, cend {{Cl|AS}} {{Cl|SINGLE}}
{{Cl|DIM}} xrot {{Cl|AS}} {{Cl|INTEGER}}, yrot {{Cl|AS}} {{Cl|INTEGER}}, SCALE {{Cl|AS}} {{Cl|INTEGER}}, pan {{Cl|AS}} {{Cl|INTEGER}}
cstart = 0: cend = 6.2
xrot = 6: yrot = 6: SCALE = 3: pan = 30
{{Cl|OUT}} {{Cl|&H}}3C8, 1: {{Cl|OUT}} {{Cl|&H}}3C9, 10: {{Cl|OUT}} {{Cl|&H}}3C9, 10: {{Cl|OUT}} {{Cl|&H}}3C9, 60
DO
  row = 2
  DO
    DO
      {{Cl|FOR...NEXT|FOR}} i = cend {{Cl|TO}} cstart {{Cl|STEP}} -.03
        x = (SCALE * 60 - (row * xrot / 4)) * {{Cl|TAN}}({{Cl|COS}}(i))
        y = {{Cl|SIN}}(SCALE * 60 - (row * yrot)) * {{Cl|TAN}}({{Cl|SIN}}(i)) * pan
        cnt = cnt + 1
        {{Cl|IF...THEN|IF}} word(cnt, row) > 0 {{Cl|THEN}} 
          {{Cl|CIRCLE}} (x + 320, y + 220), SCALE + 1, 1              'circled letters
          '{{Cl|LINE}} (x + 320, y + 220)-{{Cl|STEP}}(12, 12), 1, BF  'boxed letters
        {{Cl|END IF}}
        {{Cl|IF...THEN|IF}} cnt = {{Cl|LEN}}(text$) * 8 {{Cl|THEN}} cnt = 0: {{Cl|EXIT DO}}
      {{Cl|NEXT}}
    {{Cl|LOOP}}
    row = row + 1
  {{Cl|LOOP}} {{Cl|UNTIL}} row = 16
  cend = cend + .1
  cstart = cstart + .1
  now! = {{Cl|TIMER}}
  DO
    newnow! = {{Cl|TIMER}}
  {{Cl|LOOP}} {{Cl|UNTIL}} newnow! - now! >= .15
  {{Cl|LINE}} (1, 100)-(639, 280), 0, BF
{{Cl|LOOP}} {{Cl|UNTIL}} {{Cl|INKEY$}} = {{Cl|CHR$}}(27)
{{Cl|END SUB}} '' ''
{{CodeEnd}}
{{small|Code by Unseen Machine}}


{{PageSeeAlso}}
* [[_PI]] {{text|(QB64 function)}}
* [[SIN]], [[COS]]
* [[ATN]] {{text|(arctangent)}}
* [[Mathematical Operations]]
* [[Text Using Graphics]]
* [[Mathematical_Operations#Derived_Mathematical_Functions|Derived Mathematical Functions]]


{{PageNavigation}}
<