Absolute value

Distance from the origin on a number line.
In short, a number with positive values left unchanged and negative values made positive.

 power = pow(number, exponent);

 #include <stdio.h>
#include <stdlib.h>

void main(void)
{
    printf("%d\n", abs(10));
    printf("%d\n", abs(-10));

    return;
}

 #include <stdio.h>
#include <stdlib.h>

void main(void)
{
    printf("%d\n", abs(10));
    printf("%d\n", abs(-10));

    return;
}

 #include <math.h>
#include <stdio.h>

void main(void)
{
    printf("%d squared of %d = %f\n", 5, 2, pow(5, 2));
    printf("%d squared of %d = %f\n", 8, 3, pow(8, 3));
    printf("%d squared of %d = %f\n", 2, 10, pow(2, 10));

    return;
}

Square root

A number that, when squared, becomes that number.
If the original number is the area of the square, the square root is the length of the sides.

 Square root = sqrt(number);

 #include <math.h>
#include <stdio.h>

void main(void)
{
    printf("√%d = %f : %f * %f = %f\n", 100, sqrt(100), sqrt(100), sqrt(100), sqrt(100) * sqrt(100));
    printf("√%d = %f : %f * %f = %f\n", 2, sqrt(2), sqrt(2), sqrt(2), sqrt(2) * sqrt(2));

    return;
}

 Tangent = tan(radian angle);

Radian

A unit of angle where the position where the length of the arc and the radius are equal is one radian.
In the computer world, radians are used in most cases.

 #define RADIAN(ARC) ((ARC)*3.14159 / 180)

 #include <math.h>
#include <stdio.h>

#define RADIAN(ARC) ((ARC)*3.14159 / 180)

void main(void)
{
    double stature = 160;
    double distance = 500;
    double arc = 40;
    double tree;

    tree = distance * tan(RADIAN(arc)) + stature;
    printf("%fm\n", tree / 100);

    return;
}