Toán Lớp 10: cos $\alpha$ =1/3
Tính P=sin^2 $\alpha$ +3cos^2 $\alpha$
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Toán Lớp 10: cos $\alpha$ =1/3
Tính P=sin^2 $\alpha$ +3cos^2 $\alpha$
Comments ( 2 )
\cos\alpha = \dfrac13\\
P = \sin^2\alpha + 3\cos^2\alpha\\
\to P = (\sin^2\alpha + \cos^2\alpha) + 2\cos^2\alpha\\
\to P = 1 + 2\cdot \left(\dfrac13\right)^2\\
\to P = 1 + \dfrac29\\
\to P =\dfrac{11}{9}
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