Update README.md

README.md

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         ~~~
 
 # project - STEP 2
+### 1. list of functions
+- a. MUL ( x )
+- b. DIV ( / )
+- c. SINE
+
+### 2. explanation of fuctions
+- a. mul
+  - fx32_mul
+  ~~~
+  (fixed32)((fa * fb) >> FX32_QNUM ) 
+  ~~~
+    - fuction that multiplies fa and fb and divides it by 2^32
+  - fx32_mul1
+  ~~~
+  ((fixed32)(((fa>>16) * fb)>>16))
+  ~~~
+    - Same as fx32_mul, the same fuction as fa*fb>>32, first multiply fa/2^16 and fb, and divide the remaining 2^16
+  - fx32_mul2
+  ~~~
+  ((fixed32)(((fa>>8)*(fb>>8))>>16))
+  ~~~
+    - Same as above, the same fuction as fa*fb>>32, first multiply fa/2^8, fb/2^8, and divide the remaining 2^16
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