Question

cos(x-y) =-1 then cosx+cosy =?​

Answer 1

Answer:

Anklld

Step-by-step explanation:

if tan (A+B)=3, tan A=1/3 find tan B

Answer 2

Answer: 0

Step-by-step explanation:

$cos(x-y)=-1\\cos(x-y)=cos\pi \\x-y=\pi$

$cos x + cosy\\cos(\pi +y)+cosy\\-cosy+cosy\\0$