commit d90eecd9bb52086ee0c9278377af4d3579134f58
Author: NaiJi <naijiworld@gmail.com>
Date:   Sun Jul 19 20:40:30 2020 +0300

    Add 1.2, 1.3 and 1.7 exs

diff --git a/sicp-ex-1.2.rkt b/sicp-ex-1.2.rkt
new file mode 100644
index 0000000..9663a3e
--- /dev/null
+++ b/sicp-ex-1.2.rkt
@@ -0,0 +1,7 @@
+(define the-numerator
+  (+ 5 4 (- 2 (- 3 (+ 6 (/ 4 5))))))
+
+(define the-denominator
+  (* 3 (- 6 2)(- 2 7)))
+
+(/ the-numerator the-denominator)
\ No newline at end of file
diff --git a/sicp-ex-1.3.rkt b/sicp-ex-1.3.rkt
new file mode 100644
index 0000000..55c32e9
--- /dev/null
+++ b/sicp-ex-1.3.rkt
@@ -0,0 +1,11 @@
+(define (square x) (* x x))
+(define (sum-of-squares x y) (+ (square x) (square y)))
+(define (is-first-least? a b c) (and (< a b) (< a c)))
+
+(define a 9)
+(define b 1)
+(define c 10)
+
+(cond ((is-first-least? c a b)(sum-of-squares a b))
+      ((is-first-least? a c b)(sum-of-squares c b))
+      ((is-first-least? b a c)(sum-of-squares a c)))
\ No newline at end of file
diff --git a/sicp-ex-1.7.rkt b/sicp-ex-1.7.rkt
new file mode 100644
index 0000000..b2bd89e
--- /dev/null
+++ b/sicp-ex-1.7.rkt
@@ -0,0 +1,23 @@
+(define (sqrt-iter guess guess-prev x) 
+  (if (good-enough? guess guess-prev) 
+      guess 
+      (sqrt-iter (improve guess x) guess 
+                 x))) 
+
+(define (improve guess x)
+  (average guess (/ x guess)))
+
+(define (average x y)
+  (/ (+ x y) 2))
+
+(define (good-enough? guess guess-prev) 
+  (< (abs (- guess guess-prev)) 0.001)) 
+
+(define (sqrt-new x)
+  (if (= x 0) x (sqrt-iter 1.0 999 x)))
+
+(sqrt-new 16)
+(sqrt-new 1.0004)
+(sqrt-new 1)
+(sqrt-new 134895724398)
+(sqrt-new 0)