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

Toán Lớp 9: A=$\frac{1+ 2sinα.cosα }{cos^{2}α-sin^{2}α}$

Toán Lớp 9: A=$\frac{1+ 2sinα.cosα
}{cos^{2}α-sin^{2}α}$

Comments ( 2 )

  1. ${A = \frac{1+ 2sinα.cosα}{cos²α−sin²α}}$
    ${= \frac{cos²α+sin²α+ 2sinα.cosα}{(cosα+sinα)(cosα-sinα)}}$
    ${= \frac{(cosα+sinα)²}{(cosα+sinα)(cosα-sinα)}}$
    ${= \frac{cosα+sinα}{cosα-sinα}}$

  2. #tnvt
    A=\frac{1+2sina .cosa}{cos^2a-sin^2a}
    =\frac{sin^2a+cos^2a+2sina.cosa}{(cosa-sina)(cosa+sina)}
    =\frac{(sina+cosa)^2}[(cosa-sina)(cosa+sina)}
    =\frac{sina+cosa}{cosa-sina}

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

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