Answer:
.
Step-by-step explanation:
All coterminal angles of an angle 
are defined as
or 
where, n is an integer.
The given angle is
So, all coterminal angles of an angle are
For n=1,
Since, between 0 and 2π, therefore, the required coterminal angle is .
Answer: it is a direct variation.
Justification:
In a direct variation the variables are related by a proportionality constant in this way:
y = k x
Tthan means that the value of y is always the product of a constant times the value of x.
The situation discribed for the coal may be written as:
number of tons of coal burned: c
number of hours: h
⇒ c = k × h
Which is that you can calcualte the number of tons of coal burned at any time, once you know the proportionality constant k.
The slope is negative as it slopes to the left
using the extremities of the line:-
-(10+10 / (10 + 10) = -1
slope is -1.
