cho tam giac ABC co ABC = 70 do , ACB = 40 do . ve tia Cx la tia doi cua tia CB , vẽ tia Cy la tia phan giac cua goc ACx 1 tinh ACx , xCy . 2 CMR AB//Cy ( min

Question

cho tam giac ABC co ABC = 70 do , ACB = 40 do . ve tia Cx la tia doi cua tia CB , vẽ tia Cy la tia phan giac cua goc ACx  1 tinh ACx , xCy . 2 CMR AB//Cy ( minh can gap a)

phiduc2007thcsdt · Answer

a) Vì $Cx$ là tia đối $CB$
$→\widehat{ACB}+\widehat{ACx}=180^o$ (kề bù)
mà $\widehat{ACB}=40^o$
$→\widehat{ACx}=180^o-40^o=140^o$
Vì $Cy$ là tia phân giác $\widehat{ACx}$
$→\widehat{xCy}=\dfrac{\widehat{ACx}}{2}=\dfrac{140^o}{2}=70^o$
b) $\widehat{xCy}=70^o$
$→\widehat{xCy}=\widehat{ABC}=70^o$
mà 2 góc ở vị trí đồng vị
$→AB//Cy$

thuy64921 · Answer

a) Ta có: A&#x005E;+B&#x005E;+C&#x005E;=180o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">Aˆ+Bˆ+Cˆ=180 độ ( vì 3 góc của 1 tam giác bằng 180o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">180o180o )
&#x21D2;A&#x005E;+70o+40o=180o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒Aˆ+70 độ+40 độ=180 độ
&#x21D2;A&#x005E;+110o=180o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒Aˆ+110 độ=180 độ
&#x21D2;A&#x005E;=70o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒Aˆ=70 độ
Ta lại có: A&#x005E;+B&#x005E;=ACx&#x005E;" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">Aˆ+Bˆ=ACxˆ ( vì góc ngoài của một tam giác bằng tổng 2 góc trong không kề với nó )
&#x21D2;ACx&#x005E;=70o+70o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒ACxˆ=70 độ+70 độ
ACx&#x005E;=140o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">ACxˆ=140 độ
b) Vì Cy là tia phân giác của góc ACx&#x005E;" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">ACxˆACx^ nên:
ACy&#x005E;=12ACx&#x005E;=70o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">ACyˆ=12ACxˆ=70 độ
Ta thấy ACy&#x005E;=A&#x005E;=70o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">ACyˆ=Aˆ=70độ và 2 góc này ở vị trí so le trong nên AB // Cy
Vậy a) ACx&#x005E;=140o" role="presentation" style="box-sizing: border-box; display: inline; font-style: normal; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">ACxˆ=140 độ
        b) AB // Cy

cho tam giac ABC co ABC = 70 do , ACB = 40 do . ve tia Cx la tia doi cua tia CB , vẽ tia Cy la tia phan giac cua goc ACx 1 tinh ACx , xCy . 2 CMR AB//Cy ( minh can gap a)

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cho tam giac ABC co ABC = 70 do , ACB = 40 do . ve tia Cx la tia doi cua tia CB , vẽ tia Cy la tia phan giac cua goc ACx 1 tinh ACx , xCy . 2 CMR AB//Cy ( minh can gap a)

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