(new-plot)
(def shift .7)
(func f(x)
      (if (x < (-3 * pi / 2 - shift))
	  0
	(
	 (if (x < (3 * pi / 2 - shift))
	     (1 - sin (x + shift))
	   0)
	 )
	)
      )
(plot f (calc -3 * pi / 2 - shift) (calc (3 * pi / 2 - shift)))
(integral f-int f 0 x .01) 
(plot f f-int -6  4)
;; approximately (calc -3 * pi / 2 - shift) (calc (3 * pi / 2 - shift))
(new-plot)
(func f(x)
      (if (x < 10)
	  (- x - 10)
	(
	 (if (x < 15)
	     (4 * x - 60)
	   (
	    (if (x < 20)
		(2 * x - 30)
	      (-.5 * x + 20)
	      )
	    )
	   )
	 )
	)
      )
(plot f 0 50)
(integral f-int f 4 x .01) 
(plot f f-int 0 50)