Prove that a cyclic parallelogram is a rectangle.

Step-by-step explanation:

let ABCD be cyclic parallelogram.

Then ∠A=∠C

as it is cyclic so ∠A+∠C=180

∠C+∠C=180

2∠ C=180

∠C=90

So ∠A=90

similarly ∠B=∠D=90

so it is a rectangle.

b

step-by-step explanation:

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.