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91 lines
2.2 KiB
Markdown
91 lines
2.2 KiB
Markdown
The [TAN](TAN) function returns the ratio of [SIN](SIN)e to [COS](COS)ine or tangent value of an angle measured in radians.
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## Syntax
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> tangent! = **TAN(***radian_angle!***)**
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## Parameter(s)
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* The *radian_angle* must be measured in radians.
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## Description
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* To convert from degrees to radians, multiply degrees * π/180.
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* TANGENT is the gradient or slope of the circle or arc at [SIN](SIN)(θ) / [COS](COS)(θ). Do not use division when the [COS](COS) = 0 to avoid [ERROR Codes](ERROR-Codes).
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## Example(s)
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Spiraling text using the [SIN](SIN) and [TAN](TAN) functions.
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```vb
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DIM SHARED text AS STRING
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text$ = "S P I R A L"
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DIM SHARED word(1 TO LEN(text$) * 8, 1 TO 16)
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CALL analyse
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CLS
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CALL redraw
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SUB analyse
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CLS
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SCREEN 12
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COLOR 2: LOCATE 1, 1: PRINT text$
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DIM px AS INTEGER, py AS INTEGER, cnt AS INTEGER, ltrcnt AS INTEGER
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px = 1: py = 1
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DO
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word(px, py) = POINT(px, py)
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PSET (px, py), 1
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px = px + 1
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IF px = LEN(text$) * 8 THEN
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px = 1
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py = py + 1
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END IF
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LOOP UNTIL py = 16
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END SUB
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SUB redraw
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CLS
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DIM row AS INTEGER, cnt AS INTEGER, cstart AS SINGLE, cend AS SINGLE
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DIM xrot AS INTEGER, yrot AS INTEGER, SCALE AS INTEGER, pan AS INTEGER
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cstart = 0: cend = 6.2
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xrot = 6: yrot = 6: SCALE = 3: pan = 30
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OUT &H3C8, 1: OUT &H3C9, 10: OUT &H3C9, 10: OUT &H3C9, 60
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DO
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row = 2
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DO
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DO
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FOR i = cend TO cstart STEP -.03
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x = (SCALE * 60 - (row * xrot / 4)) * TAN(COS(i))
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y = SIN(SCALE * 60 - (row * yrot)) * TAN(SIN(i)) * pan
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cnt = cnt + 1
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IF word(cnt, row) > 0 THEN
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CIRCLE (x + 320, y + 220), SCALE + 1, 1 'circled letters
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'LINE (x + 320, y + 220)-STEP(12, 12), 1, BF 'boxed letters
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END IF
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IF cnt = LEN(text$) * 8 THEN cnt = 0: EXIT DO
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NEXT
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LOOP
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row = row + 1
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LOOP UNTIL row = 16
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cend = cend + .1
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cstart = cstart + .1
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now! = TIMER
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DO
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newnow! = TIMER
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LOOP UNTIL newnow! - now! >= .15
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LINE (1, 100)-(639, 280), 0, BF
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LOOP UNTIL INKEY$ = CHR$(27)
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END SUB
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```
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## See Also
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* [_PI](_PI) (QB64 function)
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* [SIN](SIN), [COS](COS)
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* [ATN](ATN) (arctangent)
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* [Mathematical Operations](Mathematical-Operations)
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* [Text Using Graphics](Text-Using-Graphics)
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* [Mathematical Operations](Mathematical-Operations)
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