Use parallelogram ABCD to answer the following. Diagonals BD and AC bisect at O.

1.measurement of angle BAD = 3y - 5
find angle BCD
2. AC = 12.8 cm
find OC

Since we have a parallelogram, the opposite angles are equal, so BCD = 3y-5

Also, the diagonals bisect each other, so OC = 1/2 AC = 6.4cm

To find the measurement of angle BCD, we can use the fact that diagonals BD and AC bisect at O. This means that the angle formed by the diagonal BD, side AB, and side AD is equal to the angle formed by the diagonal AC, side BC, and side CD.

1. To find angle BCD, let's name it x. We know that angle BAD is equal to 3y - 5. Since the diagonals bisect each other, angle BAD is also equal to angle BAO and angle DAO. So, we have:

angle BAO = angle DAO = 3y - 5

Since angle BCD is opposite angle BAO, we have:

angle BCD = 180° - angle BAO = 180° - (3y - 5)
angle BCD = 180° - 3y + 5
angle BCD = -3y + 185

Therefore, the measurement of angle BCD is -3y + 185.

2. To find the length of OC, we can use the fact that the diagonals of a parallelogram bisect each other. Since AC is a diagonal, the length of OC is half of AC.

Therefore, OC = 1/2 * AC = 1/2 * 12.8 cm.

Hence, the length of OC is 6.4 cm.