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@@ -0,0 +1,43 @@
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+;;;; solve-triangle.lisp
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+(defpackage #:solve-triangle
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+ (:use :cl)
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+ (:export #:solve-asa
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+ #:solve-ssa))
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+
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+(in-package #:solve-triangle)
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+
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+;; SAA, ASA -- Law of Sines
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+;; SSA -- Law of Sines, (or 0 1 2) solutions
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+;; SAS -- Law of Cosines
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+;; SSS -- Law of Cosines
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+
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+(defun solve-asa (anglea sidea angleb)
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+ "Solve a ASA triangle using the method of sines. Angles assumed to be in degrees."
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+ (let* ((anglec (- 180 anglea angleb))
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+ (sideb (/ (* (sin angleb)
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+ sidea)
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+ (sin anglea)))
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+ (sidec (/ (* (sin anglec)
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+ sidea)
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+ (sin anglea))))
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+ (list :angle-a anglea
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+ :angle-b angleb
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+ :angle-c anglec
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+ :side-a sidea
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+ :side-b sideb
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+ :side-c sidec)))
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+
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+(defun solve-ssa (sidea sideb anglea)
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+ "Solve an SSA triangle using the method of sines. Angles are assumed to be in degrees."
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+ (let* ((angleb (asin (/ (* sideb (sin anglea))
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+ sidea)))
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+ (anglec (- 180 anglea angleb))
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+ (sidec (/ (* (sin anglec)
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+ sidea)
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+ (sin anglea))))
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+ (list :angle-a anglea
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+ :angle-b angleb
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+ :angle-c anglec
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+ :side-a sidea
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+ :side-b sideb
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+ :side-c sidec)))
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