Bài 2: Mặt cầu
Hướng dẫn giải Hoạt động 4 (Trang 48 SGK Toán Hình học 12)
<p><strong class="content_question">Đề b&agrave;i</strong></p> <p>Cho h&igrave;nh lập phương ngoại tiếp mặt cầu b&aacute;n k&iacute;nh r cho trước. H&atilde;y t&iacute;nh thể t&iacute;ch của h&igrave;nh lập phương đ&oacute;.</p> <div class="content_method_container"> <p class="content_method_header"><strong class="content_method">Phương ph&aacute;p giải - Xem chi tiết</strong><img id="method_colapse_icon" class="method-open-icon" src="data:image/png;base64,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" /></p> <div class="content_method_content"> <p>Dựng h&igrave;nh, nhận x&eacute;t cạnh h&igrave;nh lập phương v&agrave; t&iacute;nh thể t&iacute;ch.</p> </div> </div> <p><strong class="content_detail">Lời giải chi tiết</strong></p> <p><img class="wscnph" style="max-width: 100%;" src="https://static.colearn.vn:8413/v1.0/upload/library/29012023/imade-5-ODLRio.jpg" width="205" height="176" /></p> <p>H&igrave;nh lập phương ngoại tiếp mặt cầu b&aacute;n k&iacute;nh <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>r</mi></math> c&oacute; cạnh bằng&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn><mi>r</mi></math>&nbsp;</p> <p>Thể t&iacute;ch h&igrave;nh lập phương đ&oacute; l&agrave;:&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>V</mi><mo>=</mo><msup><mfenced><mrow><mn>2</mn><mi>r</mi></mrow></mfenced><mn>3</mn></msup><mo>=</mo><mn>8</mn><msup><mi>r</mi><mn>3</mn></msup></math> .</p>
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