You learn all about these when you study Geometry in Secondary/High School.

Complicated Maths;

When you go do University to study Engineering you learn harder Maths like the following;

Engineers use Maths like this when they are designing, Rockets, Spacecraft, Satellites, Computers, Skyscrapers, Video Games, Hospital Equipment, Cars, Televisions, and so on.

So, you can see that it is very important to practice your Maths in school if you want to become an Engineer!