my-sin.cl

; my own sin and cos functions using taylor seris

(defun eval-poly (coef x)
	; horners method
	(prog* ((i (- (length coef) 1))
			(acc (aref coef i)))
         accum
		 (decf i)
	     (if (< i 0) (return acc))
		 (setf acc (+ (aref coef i) (* x acc)))
		 (go accum)))

(defun my-cos (x)
	(eval-poly
		#(1 0 -1/2 0 1/24 0 -1/720)
		(rem x (/ pi 2))))

(defun my-sin (x) (my-cos (- x (/ pi 2))))