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+#lang scheme
+
+;; circlearea
+;;
+;; find the area of a circle with radius r
+(define
+  (circlearea r)
+  (* 3.142 (expt r 2))
+)
+
+;; between?
+;;
+;; check whether a is between x and y
+(define
+  (between? a x y)
+  (if
+   (or
+    (and (< y a) (> x a)) ;; y < a < x
+    (and (> y a) (< x a)) ;; x < a < y
+   )
+   #t
+   #f
+  )
+)
+
+;; shorter
+;;
+;; returns the list with fewer elements
+(define
+  (shorter a b)
+  (if
+   (< (length a) (length b))
+   a
+   b
+ )
+)
+
+;; righttri?
+;;
+;; checks whether 3 integers can be the side lengths
+;; of a right triangle.
+(define
+  (righttri? a b c)
+  (cond
+    ;; a is largest (b^2 + c^2 = a^2)
+    [ (and (> a b) (> a c)) (= (+ (expt b 2) (expt c 2)) (expt a 2)) ]
+    
+    ;; b is largest (a^2 + c^2 = b^2)
+    [ (and (> b a) (> b c)) (= (+ (expt a 2) (expt c 2)) (expt b 2)) ]
+    
+    ;; c is largest (a^2 + b^2 = c^2)
+    [ (and (> c a) (> c b)) (= (+ (expt a 2) (expt b 2)) (expt c 2)) ]
+  )
+)
+\ No newline at end of file