1. The document discusses various mathematical functions in C language such as trigonometric, logarithmic, exponential and power functions. It provides examples of using functions like sin, cos, sqrt, exp, pow in a C program. 2. Character handling functions and string functions are also covered. Examples of character classification functions like isalpha and string functions like strlen, strcmp are given. 3. The document explains user-defined functions in C - how to define, call and pass arguments to functions. Examples of functions that return or not return values are provided.

2. ก C
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7.1 ก (standard functions)
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header file C ' ก1 $ % 0 2) () ) ก3 *.h * & )( *% ก %
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ก : (library functions)

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7.1.1 ก (mathematic functions)
#, ก ( % ก ' = '=-*> * 0 ก ( %
ก # *% %' ( #include <math.h> 0 ก "6* *% /
# 0ก ) 0 * 0# ( % ก # *% )
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ก / /% )6 #, double ก
ก !
acos(x) asin(x) atan(x)
sin(x) cos(x) tan(x)
sqrt(x) exp(x) pow(x,y)
log(x) log10(x) ceil(x)
floor(x) fabs(x)

4. 1) ก acos(x)
#, ก ( %' = ' arc cosine / x !" ( x #, ' )3)
" !" (radian)
6#0
acos(x);
2) ก asin(x)
#, ก ( %' = ' arc sine / x !" ( x #, ' )3)
" !"
6#0
asin(x);
3) ก atan(x)
#, ก ( %' = ' arc tan / x !" ( x #, ' )3)
" !"
6#0
atan(x);

5. 4) ก sin(x)
#, ก ( %' = ' sine / x !" ( x #, ' )3) " !"
6#0
sin(x);
5) ก cos(x)
#, ก ( %' = ' cosine / x !" ( x #, ' )3) "
!"
6#0
cos(x);
6) ก tan(x)
#, ก ( %' = ' tan / x !" ( x #, ' )3) " !"
6#0
tan(x);

6. 9( ' ) /% ก % ก acos(x), asin(x), atan(x), sin(x),
cos(x) 0 tan(x) ) ก"-( / %>ก # 0ก )* " * $# "# $ก %&'
7.1 0 ! ก % ก acos(x), asin(x), atan(x), sin(x),
cos(x) 0 tan(x)
* math1.c */
#include<stdio.h> /* ! ( 1 */
#include<math.h> /* ! ( 2 */
#include<conio.h> /* ! ( 3 */
void main(void) /* ! ( 4 */
{ /* ! ( 5 */
double r, pi = 3.141592654; /* ! ( 6 */
r = pi/180; /* ! ( 7 */
clrscr(); /* ! ( 8 */
printf("%fn",asin(r)); /* ! ( 9 */
printf("%fn",acos(r)); /* ! ( 10 */
printf("%fn",atan(r)); /* ! ( 11 */
printf("%fn",sin(r)); /* ! ( 12 */
printf("%fn",cos(r)); /* ! ( 13 */
printf("%fn",tan(r)); /* ! ( 14 */
printf("nPress any key back to program ..."); /* ! ( 15 */
getch(); /* ! ( 16 */
} /* ! ( 17 */

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8. ' ?- " # 0ก )
ก # 0ก )* " ( 7.1 ) ?- "ก / # 0ก ) ( 'N & $!%!
! ( 9 ' ( printf("%fn",asin(r)); ก ' = ' arc sin / * 0# r !" r #, )3) "
!" 0 0 ! . 9? ($!% ก 9
! ( 10 ' ( printf("%fn",acos(r)); ก ' = ' arc cosine / * 0# r !" r #, )3)
" !" 0 0 ! . 9? ($!% ก 9
! ( 11 ' ( printf("%fn",atan(r)); ก ' = ' arc tan / * 0# r !" r #, )3) "
!" 0 0 ! . 9? ($!% ก 9
! ( 12 ' ( printf("%fn",sin(r)); ก ' = ' sine / * 0# r !" r #, )3) " !"
0 0 ! . 9? ($!% ก 9
! ( 13 ' ( printf("%fn",cos(r)); ก ' = ' cosine / * 0# r !" r #, )3) "
!" 0 0 ! . 9? ($!% ก 9
! ( 14 ' ( printf("%fn",tan(r)); ก ' = ' tan / * 0# r !" r #, )3) " !"
0 0 ! . 9? ($!% ก 9
! ( 15 0 16 9-)9/% ' ) %ก!'" ! & 9( ก 6 # 0ก ) 0 "3! ' ! & ก! enter ก /% 6
# 0ก ) /* ! ( 17 */

9. 7) ก sqrt(x)
#, ก ( % ' ก ( 2 (square root) / ' ' ( * 0# x !" ( x *% #, ' ' ( -!
* / * 0# )' $)*-!
(
6#0
sqrt(x);
8) ก exp(x)
#, ก ( % ' ex !" ( x #, ' ' ( * 0# ( % #, ' "กก / e !" ( e )' # ) =
2.718282
6#0
exp(x);
9) ก pow(x,y)
#, ก ( % ' xy
!" (
x #, ' ' ( * 0# ( % #, * + 8( *% )' ) กก >6 "
y #, ' ' ( * 0# ( % #, ' "กก
6#0
pow(x, y);

10. 1.2 ก ก(" ก * ก (character functions) #, ก ( %ก /% )6 ) -! #, single char
(
( % ( 1 byte) 0 ก ( % ก # *% %' ( #include<ctype.h> 0 ก "6
* *% / # 0ก ) ) "ก % ก # $!% ก ก(" ก * ก ( 'N isalnum(ch),
isalpha(ch), isdigit(ch), islower(ch), isupper(ch), tolower(ch), toupper(ch),
isspace(ch), isxdigit(ch)
1.3 ก ก(" ก * - (string functions) #, ก ( ก /% )6 -! * - (string)
%
!"ก ( % ก # *% %' ( #include<string.h> 0 ก "6* *% / # 0ก ) "ก
"ก % ก # $!% ก ก(" ก * - ( 'N strlen(s), strcmp(s1,s2)
, strcpy(s), strcat(s1,s2)
1.4 ก ( $# ( % "&
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ก gotoxy(x,y) #, ก ( ' ( %* * 0
% (cursor) ' ( ($#" * 0 ( 3$ % 9
ก sizeof(x) #, ก ( %* / !/ * 0# x )/ !ก( Byte

11. 2. ก ( /" / (user defined functions) ก ( /" / ' "ก
# 0ก )" " ' / # 0ก ) ( /" / 9( % ) $!% " ! " ( * )' )
*% ก .6% /" # 0ก ) C -") "ก # 0ก )" " : ก : .6% ( /"
# 0ก ) # ' ' 0 -ก -") "ก : # 0ก )" ": " $ ก1* )
# 0ก )" " ก ก1) ก = ก ) ก 9" 0* "ก ( * ก
ก "ก ก 8( #, ก " 6% ก(" ก ( /"
/ (user define functions : UDF) * 0*ก # ก > 6#0 ก ก /" *
ก 0 ก "ก % ก 9( % ) % ก ( /" / # 0ก ) C $!% "
6ก*%
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ก ' $#0 ' ก $!% 3 0 '
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2.2 ก )ก ' $#0*$)) ' ก
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8( ก 0* 0 ก1 ) ก 0* " ! .6% /" ก #, ( *% >ก
' ) /% ก 0* 0 9( $!%) # "3ก* %ก $!% " ) )

12. ) ก
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3
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