What are the phase shift and period for the function y=2cos1/2(0+30*)-4

I think there is a typo here. You did not type the question correctly. I will use what you gave us to work with.

y = A sin(Bx + c) + D

Period = 2pi/B

I assume that by 0 you meant to say 0x.

Period = 2pi/0, which is undefined.

I gotta stop here because you did not give us the correct equation to work with.

step-by-step explanation: h: (- 3, 6)

m: (1, - 2)

o: (7, 6)

r: (- 9, - 2)

midpoint of hm: (- 1, 2)

midpoint of or: (- 1, 2)

therefore, b is the midpoint of both diagonals bisect each other !

to prove the diagonals are perpendicular, show that the product of the slopes = - 1