BasicsBasics• You must include the header file in

your program– # include < >

• Then use the needed function by calling it

• You must know the parameters and the return type

Most used headersMost used headers• stdio.h

• string.h

• stdlib.h

• math.h

• graphics.h

• …

Functions in math.hFunctions in math.h• sin• cos• tan• acos• asin• atan• log• pow• …

Parameter and return typeParameter and return type• double sin (double x)– Means the parameter is double

– Return type is also double

– So you should write-

double result, angle;

angle = 45.0 * 3.14159 / 180.0;

result = sin(angle);

Parameter and return typeParameter and return type• double sin (double x)– If you use int, it will not generate any

error• But you may lose data• Get wrong results

int result, angle;

angle = 45.0 * 3.14159 / 180.0; // angle = 0

result = sin(angle); // result = 0