Bài 2: Hình nón - Hình nón cụt - Diện tích xung quanh và thể tích của hình nón, hình nón cụt
Hướng dẫn giải Bài 26 (Trang 119 SGK Toán 9 Hình học, Tập 2)
<p>H&atilde;y điền đủ v&agrave;o c&aacute;c &ocirc; trống cho ở bản sau (đơn vị đọ d&agrave;i: cm)</p> <p><img class="wscnph" src="https://static.colearn.vn:8413/v1.0/upload/library/02032022/26-JBA0Ky.jpg" /></p> <p><strong>Giải</strong></p> <p>D&ograve;ng thứ nhất:</p> <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>5</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>10</mn><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>=</mo><mo>&#160;</mo><msqrt><msup><mn>12</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><msqrt><mn>169</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>13</mn><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><mn>3</mn><mo>,</mo><mn>14</mn><mo>.</mo><msup><mn>5</mn><mn>2</mn></msup><mo>.</mo><mn>12</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>314</mn></math></p> <p>D&ograve;ng thứ hai:</p> <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>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>16</mn><mn>2</mn></mfrac><mo>=</mo><mn>8</mn><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>=</mo><mo>&#160;</mo><msqrt><msup><mn>12</mn><mn>2</mn></msup><mo>&#160;</mo><mo>+</mo><mo>&#160;</mo><msup><mn>8</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>289</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>17</mn><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><mn>3</mn><mo>,</mo><mn>14</mn><mo>.</mo><msup><mn>8</mn><mn>2</mn></msup><mo>.</mo><mn>15</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>1004</mn><mo>.</mo><mn>8</mn></math></p> <p>D&ograve;ng thứ ba:</p> <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>7</mn><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>14</mn><mspace linebreak="newline"/><mi>h</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>l</mi><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>25</mn><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msup><mn>7</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>576</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>24</mn><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><mn>3</mn><mo>,</mo><mn>14</mn><mo>.</mo><msup><mn>7</mn><mn>2</mn></msup><mo>.</mo><mn>24</mn><mo>&#160;</mo><mo>&#8776;</mo><mo>&#160;</mo><mn>1230</mn><mo>,</mo><mn>9</mn></math></p> <p>D&ograve;ng thứ tư:</p> <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>&#160;</mo><mo>=</mo><mo>&#160;</mo><mfrac><mn>40</mn><mn>2</mn></mfrac><mo>=</mo><mn>20</mn><mspace linebreak="newline"/><mi>h</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><msup><mi>l</mi><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msup><mi>r</mi><mn>2</mn></msup></msqrt><mo>=</mo><mo>&#160;</mo><msqrt><msup><mn>29</mn><mn>2</mn></msup><mo>&#160;</mo><mo>-</mo><mo>&#160;</mo><msup><mn>20</mn><mn>2</mn></msup></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><msqrt><mn>441</mn></msqrt><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>21</mn><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><mn>3</mn><mo>,</mo><mn>14</mn><mo>.</mo><msup><mn>20</mn><mn>2</mn></msup><mo>.</mo><mn>21</mn><mo>&#160;</mo><mo>&#8776;</mo><mn>8792</mn></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/02032022/261-Phfp6g.jpg" /></p>
Hướng dẫn Giải Bài 26 (Trang 120, SGK Toán Hình học 9, Tập 2)
GV: GV colearn
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Hướng dẫn Giải Bài 26 (Trang 120, SGK Toán Hình học 9, Tập 2)
GV: GV colearn