If a / b equals cos A / cos B, then what triangle is it

If a / b equals cos A / cos B, then what triangle is it

According to the sine theorem, we change a and B into Sina and SINB, that is, Sina / SINB = cosa / CoSb
The result is as follows: Sina / cosa = SINB / CoSb
So Tana = tanb
Because in a triangle, all three angles are less than 180 degrees. So angle a = angle B
So it's an isosceles triangle

Cos (a + b) = why is it equal to - cos C

It's in the triangle
cos(a+b)
=cos(180-c)
=-cosC
This is the induction formula
cos(180-x)= -cosx

-What degree is 3 / 3 π equal to? What is cos?

-Three thirds of PI equals - π = - 180 degrees
Cos-180 = cos 180 = - 1