Peter sold 60 pencils at 5 for $1.20. How much money do he make
2 answers:
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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.
i)
ii)
iii)
Also, we have know that
Thus,
By (ii) and (iii) we have:
by simplifying
Now,
