$12.80 × 1.075 = $13.76
$13.76 × 1.15 =$15.82
x^2 - 7x + 15
_________________
(x+4)/ x^3 - 3x^2 - 13x + 78
- x^3 + 4x^2
----------------
- 7x^2 - 13x
- - 7x^2 - 28x
------------------
15x + 78
- 15x + 60
-------------
18
remainder = 18
<span>So you have composed two functions,
</span><span>h(x)=sin(x) and g(x)=arctan(x)</span>
<span>→f=h∘g</span><span>
meaning
</span><span>f(x)=h(g(x))</span>
<span>g:R→<span>[<span>−1;1</span>]</span></span>
<span>h:R→[−<span>π2</span>;<span>π2</span>]</span><span>
And since
</span><span>[−1;1]∈R→f is defined ∀x∈R</span><span>
And since arctan(x) is strictly increasing and continuous in [-1;1] ,
</span><span>h(g(]−∞;∞[))=h([−1;1])=[arctan(−1);arctan(1)]</span><span>
Meaning
</span><span>f:R→[arctan(−1);arctan(1)]=[−<span>π4</span>;<span>π4</span>]</span><span>
so there's your domain</span>
