September 2017 Update

Task/Animate-a-pendulum/Smart-BASIC/animate-a-pendulum.smart

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+'Pendulum
+'By Dutchman
+' --- constants
+g=9.81 ' accelleration of gravity
+l=1 ' length of pendulum
+GET SCREEN SIZE sw,sh
+pivotx=sw/2
+pivoty=150
+' --- initialise graphics
+GRAPHICS
+DRAW COLOR 1,0,0
+FILL COLOR 0,0,1
+DRAW SIZE 2
+' --- initialise pendulum
+theta=1 ' initial displacement in radians
+speed=0
+' --- loop
+DO
+  bobx=pivotx+100*l*SIN(theta)
+  boby=pivoty-100*l*COS(theta)
+  GOSUB Plot
+  PAUSE 0.01
+  accel=g*SIN(theta)/l/100
+  speed=speed+accel
+  theta=theta+speed
+UNTIL 0
+END
+' --- subroutine
+Plot:
+REFRESH OFF
+GRAPHICS CLEAR 1,1,0.5
+DRAW LINE pivotx,pivoty TO bobx,boby
+FILL CIRCLE bobx,boby SIZE 10
+REFRESH ON
+RETURN