doc; update fSin function

docs/library/fsin.bas.md

@@ -22,20 +22,17 @@ FUNCTION fSin(num as FIXED) as FIXED
 DIM quad as byte
 DIM est1,dif as uByte
 
-num = num MOD 360 
 'This change made now that MOD works with FIXED types.
-'This is much faster than the repeated subtraction method for large angles (much > 360) 
+'This is much faster than the repeated subtraction method for large angles (much > 360)
 'while having some tiny rounding errors that should not significantly affect our results.
 'Note that the result may be positive or negative still, and for SIN(360) might come out
 'fractionally above 360 (which would cause issued) so the below code still is required.
 
-while num>=360
-  num=num-360
-end while
-
-while num<0
-  num=num+360
-end while
+IF num >= 360 THEN
+  num = num MOD360
+ELSEIF num < 0 THEN
+  num = 360 - ABS(num) MOD 360
+END IF
 
 IF num>180 then
   quad=-1
@@ -63,7 +60,7 @@ sinetable:
 asm
 DEFB 000,009,018,027,035,044,053,062
 DEFB 070,079,087,096,104,112,120,127
-DEFB 135,143,150,157,164,171,177,183 
+DEFB 135,143,150,157,164,171,177,183
 DEFB 190,195,201,206,211,216,221,225
 DEFB 229,233,236,240,243,245,247,249
 DEFB 251,253,254,254,255,255
@@ -86,4 +83,3 @@ FUNCTION fTan(num as FIXED) as FIXED
     return fSin(num)/fSin(90-num)
 END FUNCTION
 ```
-