Cho tam giác ABC có góc C=1/3 góc B;góc B=góc A/2.Tính góc A

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Cho tam giác ABC có góc C=1/3 góc B;góc B=góc A/2.Tính góc A

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Ayla 2 giờ 2021-09-08T04:45:39+00:00 1 Answers 0 views 0

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    2021-09-08T04:47:07+00:00

    $\text{ Ta có: }$

    $\text{góc C=1/3 góc B; }$

    .

    $\text{Ta cũng có: }$

    $\text{góc B=góc A/2 }$

    $\text{=> góc A = 2 góc B }$

    .

    $\text{Xét tam giác ABC ta có: }$

    $\text{góc A + góc B + góc C = 180 độ }$

    $\text{<=> 2 góc B + góc B + 1/3 góc B = 180 độ }$

    $\text{<=> 10/3 góc B = 180 độ }$

    $\text{=> góc B = 54 độ }$

    $\text{=> góc A = 2.54 = 108 độ }$

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