Small code commonly used in C language

Pi

Tan (PI/4) =1 and Pi=4*arctan (1)

The inverse tangent function arctan () is represented in the C language as Atan (), and the code to ensure the accuracy of pi is as follows:

　　

Const Double 4.0 * ATAN (1.0);

Rounded

Sometimes we need to avoid floating-point error by rounding. If 100 after the radical operation should be 10, but the SQRT function is "accidentally" to 99.999, in order to avoid affecting our program, need to be rounded. The floor () function is used here to return the integer part of a number, which is rounded down. The rounding code is as follows:

　　

0.5 );    // rounding x to get y

Small code commonly used in C language