Please someone help me...

 see proof below

Step-by-step explanation:

Use the following Sum Identities:

cos (A + B) = cosA · cosB - sinA · sinB

sin (A + B) =  sinA · cos B - cosA · sinB

Use the Unit Circle to evaluate the following:

cos 30 = √3/2                            sin 30 = 1/2

cos 45 = √2/2                            sin 45 = √2/2

cos 120 = -1/2                             sin 120 = √3/2

cos 240 = -1/2                             sin 240 = -√3/2                        

cos 315 = √2/2                           sin 315 = -√2/2        

cos 330 = √3/2                          sin 330 = -1/2

Proof LHS → RHS

LHS = RHS:

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

1) c 2143.6 cm

2) c 113.0 m

3) a 33.5 ft

4)   d 2 cm

5) c 20 mm

6) 180 in

7) d 120 ft