Chapter 5: Problem 47
\(|\sin 2 \mathrm{x}|=|\mathrm{x}|-\mathrm{a}\) \(|\mathbf{x}|-\mathrm{a}>1 \quad\) for no solution \(|x|>1+a\)
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Chapter 5: Problem 47
\(|\sin 2 \mathrm{x}|=|\mathrm{x}|-\mathrm{a}\) \(|\mathbf{x}|-\mathrm{a}>1 \quad\) for no solution \(|x|>1+a\)
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\(y=\frac{x^{2}}{4}-2\) \(\frac{d y}{d x}=\frac{x}{2}\) \(\left(y-\frac{x_{\perp}^{2}}{4}+2\right)=\frac{-2}{x}\left(x-x_{1}\right)\) \(-1-\frac{x_{1}^{2}}{4}+2=\frac{-2}{x_{1}}\left(1-x_{1}\right)\) \(\Rightarrow 2 x_{1}-\frac{x_{1} 3}{4}=-2+2 x_{1}\) \(x_{1}^{3}=8\) \(x_{1}=2, \quad y=-1\)
\(y=6-x-x^{2}\) \(\frac{d y}{d x}=-1-2 x\) eqn of tangent $y-6+x_{1}+x_{1}^{2}=-\left(1+2 x_{1}\right)\left(x-x_{1}\right)$ \(x y=x+3\) \(x \frac{d y}{d x}+y=1\) \(\frac{d y}{d x}=\frac{1-y_{2}}{x}\) eqn of tangent \(\rightarrow\) \(y-\frac{x_{2}+3}{x_{2}}=\frac{1-\frac{x_{2}+3}{x_{2}}}{x_{2}}\left(x-x_{2}\right)\) \(x_{2} y-\left(x_{2}+3\right)=\frac{-3}{x_{2}}\left(x-x_{2}\right)\) Comparing the two eqns $\frac{1}{x_{2}}=\frac{-\left(1+2 x_{1}\right)}{-\frac{3}{x_{2}}}=\frac{x_{1}\left(1+2 x_{1}\right)+6-x_{1}-x_{1}^{2}}{3+x_{2}+3}$ $\frac{1}{x_{2}}=\frac{x_{2}\left(1+2 x_{1}\right)}{3} \& \frac{1}{x_{2}}=\frac{x_{1}^{2}+6}{x_{2}+6}$ \(3=x_{2}^{2}+2 x_{1} x_{2}^{2} \quad\) \& \(x_{2}+6=x_{1}^{2} x_{2}+6 x_{2}\) $3=\left(1+2 \mathrm{x}_{1}\right) \mathrm{x}_{2}^{2} \quad \& \quad \mathrm{x}_{2}=\frac{6}{5-\mathrm{x}_{1}^{2}}$ \(\Rightarrow 3=\frac{\left(1+2 x_{1}\right) 36}{\left(5-x_{1}^{2}\right)^{2}}\) $\Rightarrow\left(5-\mathrm{x}_{1}^{2}\right)^{2}=12\left(1+2 \mathrm{x}_{1}\right)$ Let \(\mathrm{y}=\mathrm{mx}+\mathrm{c}\) be the common tangent \(m x+c=6-x-x^{2}\) \(\Rightarrow \mathrm{x}^{2}+(\mathrm{m}+1) \mathrm{x}+(\mathrm{c}-6)=0\) \(\mathrm{D}=0\) \((m+1)^{2}-4(c-6)=0\) For \(x y=x+3\) \(x(m x+c)=x+3\) \(m x^{2}+(c-1) x-3=0\) \(\mathrm{D}=0\) \((c-1)^{2}+12 m=0\) Using (I) \& (II) \((m+1)^{2}+24=4 c\) \(\mathrm{c}-1=\frac{(\mathrm{m}+1)^{2}+20}{4}\) $\Rightarrow\left(\frac{(\mathrm{m}+\mathrm{l})^{2}+20}{4}\right)^{2}+12 \mathrm{~m}=0$ \(\left((m+1)^{2}+20\right)^{2}+192 m=0\) Upon solving, \(\mathrm{m}=-3\) \(\Rightarrow \mathrm{c}=7\) eqn of tangent \(=y=-3 x+7\)
Ellipse \(\rightarrow \frac{x^{2}}{16}+\frac{y^{2}}{9}=1\) \(\Rightarrow \frac{x}{8} \frac{d x}{d t}+\frac{2 y}{9} \frac{d y}{d t}=1\) $\Rightarrow \frac{4 \sqrt{1-y^{2} / 9}}{8} \frac{d x}{d t}+\frac{2 y}{9} \times \frac{d y}{d x} \times \frac{d x}{d t}=1$ Now put \(\frac{d y}{d x}=1 \quad \& \quad y=1\) $\Rightarrow \frac{4}{6 \sqrt{2}} \frac{d x}{d t}+\frac{2}{9} \frac{d x}{d t}=1$ \(\Rightarrow \frac{d x}{d t}\left(\frac{\sqrt{2}}{3}+\frac{2}{9}\right)=1\) \(\Rightarrow \frac{d x}{d t}=\frac{9}{3 \sqrt{2}+2}\)
\(y=\frac{x^{2}}{4}-3 x+10\) For \(y=2-\frac{x^{2}}{4}\) eqn of tangent \(y-2=m x+m^{2}\) Solving (II) \& (I) \(m x+2+m^{2}=\frac{x^{2}}{4}-3 x+10\) \(\Rightarrow \frac{x^{2}}{4}-(m+3) x+\left(8-m^{2}\right)=0\) \(\mathrm{D}=0\) \((m+3)^{2}-\left(8-m^{2}\right)=0\) \(2 m^{2}+6 m+1=0\) \(\mathrm{m}_{1}+\mathrm{m}_{2}=-3\)
\(x^{4}+y^{4}=a^{4}\) \(x^{3}+y^{3} \frac{d y}{d x}=0\) \(\frac{d y}{d x}=\frac{-x^{3}}{y^{3}}\) eqn of tangent \(\rightarrow\) \(\mathrm{y}-\mathrm{y}_{1}=-\frac{\mathrm{x}_{1}^{3}}{\mathrm{y}_{1}^{3}}\left(\mathrm{x}-\mathrm{x}_{1}\right)\) \(\mathrm{p}=\frac{\mathrm{y}_{1}^{4}}{\mathrm{x}_{1}^{3}}+\mathrm{x}_{1}=\frac{\mathrm{x}_{1}^{4}+\mathrm{y}_{1}^{4}}{\mathrm{x}_{1}^{3}}=\frac{\mathrm{a}^{4}}{\mathrm{x}_{1}^{3}}\) \(\mathrm{q}=\mathrm{y}_{1}+\frac{\mathrm{x}_{1}^{4}}{\mathrm{y}_{1}^{3}}=\frac{\mathrm{a}^{4}}{\mathrm{y}_{1}^{3}}\) Now, \(\mathrm{p}^{-4 / 3}+\mathrm{q}^{-4 / 3}=\mathrm{a}^{-4 / 3}\)
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