Ôn tập chương III
Hướng dẫn Giải Bài 5 (trang 128, SGK Toán Giải Tích 12_Trắc nghiệm)
<p><strong>B&agrave;i 5 (trang 128, SGK To&aacute;n Giải T&iacute;ch 12_Trắc nghiệm):</strong></p> <p>Diện t&iacute;ch h&igrave;nh phẳng giới hạn bởi c&aacute;c đường cong:</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">a</mi><mo>)</mo><mo>&#160;</mo><mi mathvariant="normal">y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msup><mi mathvariant="normal">x</mi><mn>3</mn></msup><mo>&#160;</mo><mi>v&#224;</mi><mo>&#160;</mo><mi mathvariant="normal">y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msup><mi mathvariant="normal">x</mi><mn>5</mn></msup><mo>&#160;</mo><mi>b&#7857;ng</mi><mo>:</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">A</mi><mo>)</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">B</mi><mo>)</mo><mo>&#160;</mo><mo>-</mo><mn>4</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">C</mi><mo>)</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>12</mn></mfrac><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">D</mi><mo>)</mo><mo>&#160;</mo><mn>2</mn><mo>.</mo></math></p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">b</mi><mo>)</mo><mo>&#160;</mo><mi mathvariant="normal">y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mi mathvariant="normal">x</mi><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mi>sin</mi><mo>&#160;</mo><mi mathvariant="normal">x</mi><mo>&#160;</mo><mi>v&#224;</mi><mo>&#160;</mo><mi mathvariant="normal">y</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mi mathvariant="normal">x</mi><mo>&#160;</mo><mo>(</mo><mn>0</mn><mo>&#160;</mo><mo>&#8804;</mo><mo>&#160;</mo><mi mathvariant="normal">x</mi><mo>&#160;</mo><mo>&#8804;</mo><mo>&#160;</mo><mn>2</mn><mi mathvariant="normal">&#960;</mi><mo>)</mo><mo>&#160;</mo><mi>b&#7857;ng</mi><mo>:</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">A</mi><mo>)</mo><mo>&#160;</mo><mo>-</mo><mn>4</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">B</mi><mo>)</mo><mo>&#160;</mo><mn>4</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">C</mi><mo>)</mo><mo>&#160;</mo><mn>0</mn><mo>&#160;</mo><mo>;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>&#160;</mo><mo>(</mo><mi mathvariant="normal">D</mi><mo>)</mo><mo>&#160;</mo><mn>1</mn><mo>.</mo></math></p> <p><strong><em>Hướng dẫn giải:</em></strong></p> <p>a) <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">S</mi><mo>=</mo><msubsup><mo>&#8747;</mo><mn>0</mn><mn>1</mn></msubsup><mo>(</mo><msup><mi mathvariant="normal">x</mi><mn>3</mn></msup><mo>-</mo><msup><mi mathvariant="normal">x</mi><mn>5</mn></msup><mo>)</mo><mi>dx</mi><mo>=</mo><mo>(</mo><mfrac><msup><mi mathvariant="normal">x</mi><mn>4</mn></msup><mn>4</mn></mfrac><mo>-</mo><mfrac><msup><mi mathvariant="normal">x</mi><mn>6</mn></msup><mn>6</mn></mfrac><mo>)</mo><msubsup><mo>|</mo><mn>0</mn><mn>1</mn></msubsup><mo>=</mo><mfrac><mn>1</mn><mn>12</mn></mfrac></math>.</p> <p><em>=&gt;</em><span style="font-style: italic;">&nbsp;</span> Chọn C.</p> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">b</mi><mo>)</mo><mo>&#160;</mo><mi mathvariant="normal">S</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msubsup><mo>&#8747;</mo><mn>0</mn><mrow><mn>2</mn><mi mathvariant="normal">&#960;</mi></mrow></msubsup><mfenced open="|" close="|"><mi>sinx</mi></mfenced><mi>dx</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msubsup><mo>&#8747;</mo><mn>0</mn><mi mathvariant="normal">&#960;</mi></msubsup><mi>sinxdx</mi><mo>&#160;</mo><mo>+</mo><msubsup><mo>&#8747;</mo><mi mathvariant="normal">&#960;</mi><mrow><mn>2</mn><mi mathvariant="normal">&#960;</mi></mrow></msubsup><mo>(</mo><mo>-</mo><mi>sinx</mi><mo>)</mo><mi>dx</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mo>-</mo><mi>cosx</mi><msubsup><mo>|</mo><mn>0</mn><mi mathvariant="normal">&#960;</mi></msubsup><mo>+</mo><mi>cosx</mi><msubsup><mo>|</mo><mi mathvariant="normal">&#960;</mi><mrow><mn>2</mn><mi mathvariant="normal">&#960;</mi></mrow></msubsup><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>4</mn></math></p> <p>=&gt; Chọn B.</p>
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