Is there a teacher who is willing to explain trigonometric functions to his disciples in detail, with the parity unchanged? I just missed that class. This is very important. My understanding ability i

Is there a teacher who is willing to explain trigonometric functions to his disciples in detail, with the parity unchanged? I just missed that class. This is very important. My understanding ability is still good. Let me give you an example. For example, the tangent Sin(x+π/2) is preceded by an odd number, so if he wants to change it to the simplest form, he has to change the function name to.

Cos, so sin(x+π/2)=-cos(x). The symbol before the function name can be determined according to the quadrant where the function is located. The symbol of the function changed to the simplest form must be the same as that of the original function. The so-called "even invariance" is because the number before π is even, so he just divides by 2, and there is no remainder, which is equivalent to just turning a few times in the unit circle and returning to the original place (the radian of a circle is 2π), so his function name does not need to be changed, and the sign has not changed.