Bài 2: Hình nón - Hình nón cụt - Diện tích xung quanh và thể tích của hình nón, hình nón cụt
Hướng dẫn giải Bài 20 (Trang 118 SGK Toán 9 Hình học, Tập 2)
<p>H&atilde;y điền đủ v&agrave;o c&aacute;c &ocirc; trống ở bản sau (xem h&igrave;nh 96)</p> <p><img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/01032022/20-vYZyZU.jpg" /></p> <p><strong>Giải</strong></p> <ul> <li>D&ograve;ng thứ nhất:</li> </ul> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>d</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>2</mn><mi>r</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>2</mn><mo>.</mo><mn>10</mn><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>l</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>h</mi><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>10</mn><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mn>10</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>10</mn><msqrt><mn>2</mn></msqrt><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>V</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><msup><mi>&#960;r</mi><mn>2</mn></msup><mi mathvariant="normal">h</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><mo>.</mo><msup><mn>10</mn><mn>2</mn></msup><mo>.</mo><mn>10</mn><mo>.</mo><mi mathvariant="normal">&#960;</mi><mo>&#160;</mo><mo>=</mo><msup><mn>10</mn><mn>3</mn></msup><mo>.</mo><mi mathvariant="normal">&#960;</mi><mo>.</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><mo>&#160;</mo><mo>(</mo><msup><mi>cm</mi><mn>3</mn></msup><mo>)</mo></math></p> <ul> <li>D&ograve;ng thứ hai:</li> </ul> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>l</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>h</mi><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>10</mn><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mn>5</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>5</mn><msqrt><mn>5</mn></msqrt><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>V</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><msup><mi>&#960;r</mi><mn>2</mn></msup><mi mathvariant="normal">h</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><mi mathvariant="normal">&#960;</mi><mo>.</mo><msup><mn>5</mn><mn>2</mn></msup><mo>.</mo><mn>10</mn><mo>&#160;</mo><mo>=</mo><mn>250</mn><mo>.</mo><mi mathvariant="normal">&#960;</mi><mo>.</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><mo>&#160;</mo><mo>(</mo><msup><mi>cm</mi><mn>3</mn></msup><mo>)</mo></math></p> <ul> <li>D&ograve;ng thứ ba:</li> </ul> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>T</mi><mi>&#7915;</mi><mo>&#160;</mo><mi>V</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><msup><mi>&#960;r</mi><mn>2</mn></msup><mi mathvariant="normal">h</mi><mo>&#160;</mo><mo>&#8658;</mo><mo>&#160;</mo><mi mathvariant="normal">r</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mfrac><mrow><mn>3</mn><mi mathvariant="normal">V</mi></mrow><mi>&#960;h</mi></mfrac></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mfrac><mrow><mn>3</mn><mo>.</mo><mn>1000</mn></mrow><mrow><mi mathvariant="normal">&#960;</mi><mo>.</mo><mn>10</mn></mrow></mfrac></msqrt><mo>=</mo><mo>&#160;</mo><mn>10</mn><msqrt><mfrac><mn>3</mn><mi mathvariant="normal">&#960;</mi></mfrac></msqrt><mo>&#160;</mo><mo>(</mo><mi>cm</mi><mo>)</mo><mspace linebreak="newline"/><mi mathvariant="normal">d</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>2</mn><mi mathvariant="normal">r</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>2</mn><mo>.</mo><mn>10</mn><msqrt><mfrac><mn>3</mn><mi mathvariant="normal">&#960;</mi></mfrac></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>20</mn><msqrt><mfrac><mn>3</mn><mi mathvariant="normal">&#960;</mi></mfrac></msqrt><mo>&#160;</mo><mo>(</mo><mi>cm</mi><mo>)</mo><mspace linebreak="newline"/><mi>l</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>h</mi><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>10</mn><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mn>10</mn><mn>2</mn></msup><mfrac><mn>3</mn><mi mathvariant="normal">&#960;</mi></mfrac></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>10</mn><msqrt><mn>1</mn><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mfrac><mn>3</mn><mrow><mi mathvariant="normal">&#960;</mi><mstyle displaystyle="true"><mfrac><mrow/><mrow/></mfrac></mstyle></mrow></mfrac></msqrt><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo></math></p> <ul> <li>D&ograve;ng thứ tư:</li> </ul> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>T</mi><mi>&#7915;</mi><mo>&#160;</mo><mi>d</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>2</mn><mi>r</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>2</mn><mo>.</mo><mn>10</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>20</mn><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>V</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>1</mn><mn>3</mn></mfrac><msup><mi>&#960;r</mi><mn>2</mn></msup><mi mathvariant="normal">h</mi><mo>&#160;</mo><mo>&#8658;</mo><mi>h</mi><mo>=</mo><mo>&#160;</mo><mfrac><mrow><mn>3</mn><mi>V</mi></mrow><mrow><mi mathvariant="normal">&#960;</mi><msup><mi>r</mi><mn>2</mn></msup></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>3</mn><mo>.</mo><mn>1000</mn></mrow><mrow><msup><mn>10</mn><mn>2</mn></msup><mi mathvariant="normal">&#960;</mi></mrow></mfrac><mo>=</mo><mo>&#160;</mo><mfrac><mn>30</mn><mi mathvariant="normal">&#960;</mi></mfrac><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>l</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>h</mi><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mfenced><mfrac><mn>30</mn><mi mathvariant="normal">&#960;</mi></mfrac></mfenced><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mn>10</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>10</mn><mn>2</mn></msup><mfenced><mrow><mfrac><mn>9</mn><msup><mi mathvariant="normal">&#960;</mi><mn>2</mn></msup></mfrac><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>1</mn></mrow></mfenced></msqrt><mo>&#160;</mo><mo>=</mo><msup><mn>10</mn><mn>2</mn></msup><mo>&#160;</mo><msqrt><mfenced><mrow><mfrac><mn>9</mn><msup><mi mathvariant="normal">&#960;</mi><mn>2</mn></msup></mfrac><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><mn>1</mn></mrow></mfenced></msqrt><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo></math></p> <ul> <li>D&ograve;ng thứ năm:</li> </ul> <p><math xmlns="http://www.w3.org/1998/Math/MathML"><mi>r</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mi>d</mi><mn>2</mn></mfrac><mo>=</mo><mfrac><mn>10</mn><mn>2</mn></mfrac><mo>=</mo><mn>5</mn><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>h</mi><mo>=</mo><mo>&#160;</mo><mfrac><mrow><mn>3</mn><mi>V</mi></mrow><mrow><mi mathvariant="normal">&#960;</mi><msup><mi>r</mi><mn>2</mn></msup></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>3</mn><mo>.</mo><mn>1000</mn></mrow><mrow><mi mathvariant="normal">&#960;</mi><msup><mn>5</mn><mn>2</mn></msup></mrow></mfrac><mo>=</mo><mo>&#160;</mo><mfrac><mn>120</mn><mi mathvariant="normal">&#960;</mi></mfrac><mo>&#160;</mo><mo>(</mo><mi>c</mi><mi>m</mi><mo>)</mo><mspace linebreak="newline"/><mi>l</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>h</mi><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><msqrt><msup><mfenced><mfrac><mn>120</mn><mi mathvariant="normal">&#960;</mi></mfrac></mfenced><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mn>5</mn><mn>2</mn></msup></msqrt></math></p> <p>Điền c&aacute;c số v&agrave;o &ocirc; trống, ta được kết quả bảng sau:</p> <p><img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/01032022/201-klHMNZ.jpg" /></p>
Hướng dẫn Giải Bài 20 (Trang 119, SGK Toán Hình học 9, Tập 2)
GV: GV colearn
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Hướng dẫn Giải Bài 20 (Trang 119, SGK Toán Hình học 9, Tập 2)
GV: GV colearn