Answer:
C is the right answer I think
We have to prove that the tangent is an odd function.
If the tangent is an odd function, the following condition should be satisfied:

From the figure we can see that the tangent can be expressed as:
We can start then from tan(t) and will try to arrive to -tan(-t):

We have arrived to the condition for odd functions, so we have just proved that the tangent function is an odd function.
Answer: the number of item A that you sold is 11
the number of item B that you sold is 2
Step-by-step explanation:
Let x represent the number of item A that you sold.
Let y represent the number of item B that you sold.
The total number of item A and item B sold is 13. This means that
x + y = 13
The cost of item A is $8 and the
cost of item B is $4. The total amount if money made is $88. This means that
8x + 4y = 88 - - - - - - - - - -1
Substituting x = 13 - y into equation 1, it becomes
8(13 - y) + 4y = 88
104 - 8y = 88
8y = 104 - 88 = 16
y = 16/8 = 2
x = 13 - y = 13 - 2 = 11
I you're looking for the equation, it is

and If you need me to solve it, it is
Protons is the answer that makes the most sense