Update README.md

README.md

@@ -199,7 +199,7 @@
 - b. div
   - fx32_div
   ~~~
-  (fixed32)( (((fixed64)(fa) << FX32_QNUM) /(fb))) 
+      ( (((fixed64)(fa) << FX32_QNUM) /(fb))) 
   ~~~
      1. fuction that multiplies fa by 2^32 and divides fb.
   - fx32_div1
@@ -250,6 +250,28 @@
   }
   ~~~
     - with using sine table and sine function can derive the appropriate sine value.
+    - there are four part in sine function because it is divided from the 1st quadrant to the 4th quadrant according to the sine value.
+      - a. angle with negative value
+      ~~~
+      if ( fa < 0 ) 
+      {
+        sign = -1;
+        fa *= -1; 
+      }
+      ~~~
+      - b. 3th, 4th quadrant
+      ~~~
+      if ( fa >= FX32_180 ) 
+      {
+        sign *= -1;
+        fa -= FX32_180;
+      }
+      ~~~
+      - c. 2th quadrant
+      ~~~
+      if ( fa > FX32_90 ) 
+        fa = FX32_180 - fa;
+      ~~~
 
 ### 3. speed vertification review
 - a. mul