Cho tam giác abc vuông tại a
Chứng minh:
a c ⋅ sin b + a b ⋅ sin c = b c

The variable z is directly proportional to x, and inversely proportional to y. when x is 4 and y is 13, z has the value 1.2307692307692. what is the value of z when x= 9, and y= 20

Plz me i need i will give a brain

What numbers are included in the set of integers? what numbers are not included?