we can use
sound level formula

where
is the sound level for a noise
I is intensity given
I0 is reference intensity
we know that reference intensity as

we are given

now, we can plug these values
and we get

now, we can simplify it

................Answer
To verify the identity we need the following identities:
i)

ii)

iii)

.
Also, we have know that

and

Thus,

By (ii) and (iii) we have:

by simplifying

and

Now,

is clearly -tanx.
Answer:
Step-by-step explanation:
What
are you calculating area or circumference??
First add y to both sides to get 9x=45+y than subtract 45 from both sides to get 9x-45=y or y=9x-45