Numbers and maths

C++ as a calculator

Operator	Meaning	Example	Result
+ -	add, subtract	7 - 2	5
*	multiply	3 * 4	12
/	divide	7.0 / 2	3.5
%	remainder (ints only)	7 % 2	1

The usual order of operations applies, and parentheses group: (1 + 2) * 3 is 9.

ints and doubles

The type matters. When both sides of / are ints, C++ does integer division and throws the remainder away: 7 / 2 is 3, and 90 / 180 is 0. As soon as one side is a double, you get the real answer: 7.0 / 2 is 3.5. This catches everyone out at least once, so when a result is mysteriously 0, look for two ints being divided.

A variable that should never change can be marked const. The compiler then refuses any line that tries to change it:

const double forearm = 0.25;   // metres

Maths functions

#include <cmath> brings in std::sqrt(x) (square root), std::pow(x, 2) (powers), std::sin, std::cos and friends. #include <numbers> gives you π as std::numbers::pi. C++ has no ** operator: square a number with x * x or std::pow(x, 2).

Robots measure angles in radians. A full turn is 360°, or $2\pi$ radians, so:

$$\text{radians} = \text{degrees} \times \frac{\pi}{180}$$

Your task

The starter stores the arm's upper arm (0.30 m), forearm (0.25 m) and an angle in degrees.

1. Set reach to the two lengths added together. Use the variables, not the numbers.
2. Set angle_rad to angle_deg converted to radians. Mind the integer division.
3. Set diagonal to the length of the diagonal across a square table 0.8 m on each side: $\sqrt{0.8^2 + 0.8^2}$.

The program prints all three, and the grader reads them from the console.