電子課本網(wǎng) › 第93頁(yè)

第93頁(yè)

信息發(fā)布者：

45°

60°

?$\frac {\sqrt{3}}{2}$?

?$\frac {\sqrt{6}}{6}$?

?$解：原式=(\frac {1}{2})2+(\frac {\sqrt{3}}{2})2-\sqrt{2}×\frac {\sqrt{2}}{2}$?

? $=1-1$?

? $=0$?

?$解：原式=\frac {\sqrt{3}}{3}+1-2×\frac {1}{2}+\sqrt{3}$?

?$=\frac {\sqrt{3}}{3}+1-1+\sqrt{3}$?

?$=\frac {4\sqrt{3}}{3}$?

?$解：原式=\frac {\frac {\sqrt{2}}{2}}{\frac {\sqrt{3}}{2}+1}-\frac {\frac {\sqrt{2}}{2}}{1-\frac {\sqrt{3}}{2}}$?

?$=\frac {\frac {\sqrt{2}×(1-\frac {\sqrt{3}}{2})}{2}}{\frac {1}{4}}-\frac {\frac {\sqrt{2}}{2}×(1-\frac {\sqrt{3}}{2})}{\frac {1}{4}}$?

?$=2\sqrt{2}×[(1-\frac {\sqrt{3}}{2})-(1+\frac {\sqrt{3}}{2})]$?

?$=2\sqrt{2}×(-\sqrt{3})$?

?$=-2\sqrt{6}$?

?$解：原式=2×\frac {1}{2}+\frac {1}{3}+1-2$?

?$=1+\frac {1}{3}-1$?

?$=\frac {1}{3}$?

?$解： (1)在Rt△ABC中$?

?$因?yàn)椤螦=30°，∠C=90°，∠B=60°$?

?$因?yàn)閍=4\sqrt{3}$?

?$所以b=\frac {a}{tan_{30}°}=12，c=\frac {a}{sin_{30}°}=8\sqrt{3}$?

?$(2)在Rt△ABC中$?

?$因?yàn)閍= 6\sqrt{2}，c=12，∠C = 90°$?

?$所以b=\sqrt{c2-a2}= 6\sqrt{2}$?

?$所以sinA=\frac {a}{c}=\frac {\sqrt{2}}{2}，sinB=\frac {c}=\frac {\sqrt{2}}{2}$?

?$所以∠A=45°，∠B=45°$?

解:過(guò)點(diǎn)?$A$?作?$AE⊥BD，$?交?$BD$?的延長(zhǎng)線于點(diǎn)?$E ，$?如圖所示

?$因?yàn)镈B⊥BC， AE⊥DB$?

?$所以AE//BC，∠AED=∠DBC= 90°$?

?$所以∠EAD=∠C=30°， $?

?$所以△ADE∽△CDB$?

?$因?yàn)閈frac {AD}{DC}=\frac {1}{2}$?

?$所以\frac {AE}{BC}=\frac {DE}{DB}=\frac {1}{2}$?

?$設(shè)DE=x ，則DB=2x， BE=3x$?

?$在Rt△ADE中$?

?$因?yàn)椤螮AD=30°， DE=x$?

?$所以AE=\sqrt{3}x$?

?$所以tan∠ABD=\frac {AE}{BE}=\frac {\sqrt{3}x}{3x}=\frac {\sqrt{3}}{3}$

亚洲激情+欧美激情,无码任你躁久久久久久,我的极品美女老婆,性欧美牲交在线视频,亚洲av高清在线一区二区三区