June 2018 Update

Task/Animate-a-pendulum/BASIC/animate-a-pendulum-2.basic

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+10 GOSUB 1000
+20 THETA = π/2
+30 G = 9.81
+40 L = 0.5
+50 SPEED = 0
+60 PX = 20
+70 PY = 1
+80 BX = PX+L*20*SIN(THETA)
+90 BY = PY-L*20*COS(THETA)
+100 PRINT CHR$(147);
+110 FOR X=PX TO BX STEP (BX-PX)/10
+120 Y=PY+(X-PX)*(BY-PY)/(BX-PX)
+130 PRINT CHR$(19);LEFT$(X$,X);LEFT$(Y$,Y);"."
+140 NEXT
+150 PRINT CHR$(19);LEFT$(X$,BX);LEFT$(Y$,BY);CHR$(113)
+160 ACCEL=G*SIN(THETA)/L/50
+170 SPEED=SPEED+ACCEL/10
+180 THETA=THETA+SPEED
+190 GOTO 80
+980 REM ** SETUP STRINGS TO BE USED **
+990 REM ** FOR CURSOR POSITIONING   **
+1000 FOR I=0 TO 39: X$ = X$+CHR$(29): NEXT
+1010 FOR I=0 TO 24: Y$ = Y$+CHR$(17): NEXT
+1020 RETURN