For this case we have that by definition, the density is given by:

Where:
M: It is the mass of the diamond
V: It is the volume of the diamond
According to the data of the statement we have:

So the volume is:

Thus, the volume of the diamond is approximately 
Answer:

No. To test whether a graph is a function or not you do the vertical line test where if a vertical line touches more than one point it is not a function
.25 or 1/4 Is the simplest form
1+tan^2(A) = sec^2(A) [Pythagorean Identities]
tan^2(A)cot(A) = tan(A)[tan(A)cot(A)] = tan(A)[1] = tan(A)
*see photo for complete solution*