Hey I need help on that too. Do you want to be friends with me??
Answer: (A) CDD
if D=C^-1
then
C D D = (C C^-1) D = I D = D
(where I is the identity matrix)
Yes it is. Input the numbers into the pythagorean theorem,

and if they equal each other it is a right triangle.
Answer:
126.4 cm
Step-by-step explanation:
1. 15.8 * 3 = 47.4 (This is the length)
2. Find half of the rectangle
47.4 + 15.8 (width) = 63.2
3. Find the whole perimeter
63.2 * 2 = 126.4
i believe the answer would than have to be 17,24,31,45,52