If $20x=\pi$, what is $\frac{\cos 4x - \cos 8x}{\cos 4x\cdot \cos 8x}$? If $20x=\pi$,
what is $$\frac{\cos 4x - \cos 8x}{\cos 4x\cdot \cos 8x}?$$
I've tried using the factor formula on the numerator but I haven't managed to get anywhere with it...
This is a multiple choice question with options $4$, $2$, $1$, $-1$, and $-2$.
Thanks in advance!

$$\\ 20x=\pi \\ 10x=\frac { \pi  }{ 2 } \\ \frac { \cos { \left( 10x-6x \right) -\cos { \left( 10x-2x \right)  }  }  }{ \cos { \left( 10x-6x \right) \cos { \left( 10x-2x \right)  }  }  } =\frac { \sin { \left( 6x \right) -\sin { \left( 2x \right)  }  }  }{ \sin { \left( 6x \right) \sin { \left( 2x \right)  }  }  } =\frac { 2\sin { \left( 2x \right) \cos { \left( 4x \right)  }  }  }{ \sin { \left( 6x \right) \sin { \left( 2x \right)  }  }  } =2\frac { \cos { \left( 4x \right)  }  }{ \sin { \left( 6x \right)  }  } =2$$
