平行四邊形和梯形

1、平行四邊形和梯形執(zhí)教：黃利群一、教學(xué)內(nèi)容人教版義務(wù)教育課程標(biāo)準(zhǔn)實(shí)驗(yàn)教科書(shū)四年級(jí)上冊(cè)p.70，例1。二、教學(xué)目標(biāo)1、了解平行四邊形和梯形的定義，掌握平行四邊形和梯形的特征。2、探討長(zhǎng)方形、正方形、平行四邊形和梯形的關(guān)系。3、通過(guò)活動(dòng)，使學(xué)生逐步形成空間觀念。三、教學(xué)重難點(diǎn)1、了解平行四邊形和梯形的定義，掌握平行四邊形和梯形的特征。2、探討長(zhǎng)方形、正方形、平行四邊形和梯形的關(guān)系。四、教學(xué)準(zhǔn)備四邊形、長(zhǎng)方形、正方形、平行四邊形和梯形五、教學(xué)設(shè)計(jì)（一）復(fù)習(xí)回顧。讓學(xué)生回憶以前學(xué)過(guò)的一些幾何圖形，說(shuō)一說(shuō)都有哪些？（二）學(xué)習(xí)新課p.70例11、 讓學(xué)生畫(huà)出各種形狀和大小不同的四邊形。2、 標(biāo)出你知道的圖形

2、的名稱(chēng)。3、師出示各種四邊形。4、讓學(xué)生說(shuō)出什么叫四邊形？（由四條線段圍成的封閉圖形叫做四邊形）。在上面的圖形中哪些是你知道的圖形。（第一、二個(gè)圖形分別是長(zhǎng)方形和正方形，第三個(gè)圖形是平行四邊形，第四個(gè)圖形是梯形）。5、讓學(xué)生觀察這些圖形有什么共同特征，分組討論后在班上討論交流。6、讓學(xué)生用三角尺和直尺檢驗(yàn)第三和第四個(gè)圖形的每組對(duì)邊是否平行。7、在學(xué)生匯報(bào)的基礎(chǔ)上，概括出平行四邊形和梯形的概念。兩組對(duì)邊分別平行的四邊形叫做平行四邊形；只有一組對(duì)邊平行的四邊形叫做梯形。8、討論：長(zhǎng)方形和正方形可以看成是特殊的平行四邊形嗎？分小組討論，然后交流結(jié)果。9、分組討論：根據(jù)對(duì)邊平行的情況，你可以把四邊形分

3、成幾類(lèi)？每類(lèi)各有什么圖形？長(zhǎng)方形、正方形的兩組對(duì)邊都分別平行，都具備了平行四邊形的特征，所以屬于平行四邊形。但是長(zhǎng)方形、正方形的四個(gè)角都是直角，所以是特殊的平行四邊形。而正方形還有四條邊都相等的特征，所以說(shuō)正方形又可以看作是特殊的長(zhǎng)方形。（三）課堂小結(jié)說(shuō)一說(shuō)這節(jié)課你有什么收獲？小結(jié)：平行四邊形和梯形是兩種特殊的四邊形，我們通過(guò)學(xué)習(xí)知道了平行四邊形、梯形、長(zhǎng)方形和正方形之間的聯(lián)系和區(qū)別。c29c91afe4ced1b6c8795ad9c91afe4ced1b6c8795ad91afe4ced1b6c8795ad9c91fe4ced1b6c8795ad29c91afedd1b6c87d1b6c87

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