In Precalculus one learns about trigonometry and it explains concepts which are introductions to calculus. Calculus uses the concepts/ syllabi taught in precalculus to develop formulas for processes for finding things like derivatives. Precalculus is also called preparation for calculus.

Precalculus is not something that was invented. It is merely the things about mathematics that you need to know before you can begin the study of calculus.

there are tons of them! If you go to google news, type in precalculus you will be surprised how many you gdt.

Precalculus and/or calculus.

Veterinarians do occasionally use precalculus when practicing. This is because math and science are huge components of practicing veterinary medicine.