; Sin / Cos / Tan example. 

; Left/Right arrow keys change angle. Escape quits. 

Const width = 640, height = 480 
Const radius# = .2 * height 
Const KEY_ESC = 1, KEY_LEFT = 203, KEY_RIGHT = 205 

Graphics width, height 
SetBuffer BackBuffer( ) 
Origin width / 3, height / 2 

angle# = 0.0 

While Not KeyDown( KEY_ESC ) 

; NOTE: It is usually best to avoid very large angles. 
; The 'If angle...' lines show one way to do this. 
; Mod is another possibility. 

If KeyDown( KEY_LEFT ) Then angle = angle - .5 
; If angle < 0.0 Then angle = angle + 360 

If KeyDown( KEY_RIGHT ) Then angle = angle + .5 
; If angle >= 360.0 Then angle = angle - 360 

Cls 

Color 80, 80, 0 ; pale yellow circle 
Oval -radius, -radius, 2 * radius, 2 * radius, False 

For a# = 0.0 To Abs( angle Mod 360 ) Step .5 

x# = radius * Cos( a ) ; (x,y) is a point on the circle 
y# = radius * Sin( a ) ; corresponding to angle a. 

If ( angle Mod 360 < 0 ) Then y = -y ; reverse for negative angle 
WritePixel x, y, $ffff00 ; bright yellow 

Next 

Color 255, 255, 0 ; yellow 
Line 0, 0, radius * Cos( angle ), radius * Sin( angle ) 

Color 0, 255, 0 ; green 
Line 0, 0, radius * Cos( angle ), 0 
Text radius * 1.5, 10, "Cos( angle ) = " + Cos( angle ) 

Color 255, 0, 0 ; red 
Line radius * Cos( angle ), 0, radius * Cos( angle ), radius * Sin( angle ) 
Text radius * 1.5, -10, "Sin( angle ) = " + Sin( angle ) 

Color 255, 255, 255 
Text radius * 1.5, -30, " angle = " + angle 
Text radius * 1.5, 30, "Tan( angle ) = " + Tan( angle ) 

Flip 

Wend 

End