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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 9: Cho cot ga= 3/4 và a là góc nhọn. Tính sina,cosa,tana

Toán Lớp 9: Cho cot ga= 3/4 và a là góc nhọn. Tính sina,cosa,tana

Comments ( 2 )

  1. $tan∝=\dfrac{1}{cot∝}=\dfrac{4}{3}$
    $tan∝=\dfrac{sin∝}{cos∝}=\dfrac{4}{3}$
    $⇒sin∝=\dfrac{4}{3}cos∝$
    $sin^2∝+cos^2∝=1$
    $⇔\left ( \dfrac{4}{3}cos∝ \right )^2+cos^2∝=1$
    $⇔\dfrac{16}{9}cos^2∝+cos^2∝=1$
    $⇔\dfrac{25}{9}cos^2∝=1$
    $⇔cos∝=\dfrac{3}{5}$
    $⇒sin∝=\dfrac{4}{5}$
    Vậy $sin∝=\dfrac{4}{5} ; cos∝=\dfrac{3}{5} ; tan∝=\dfrac{4}{3}$
     

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222-9+11+12:2*14+14 = ? ( )