Giải phương trình: 2cos2x2+x2=2x+2−x.
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Cho : 2.cos2x -3 cosx -3 >0, chứng minh rằng: sin (1/cosx) < 0
Trả lời 01-10-18 01:34 PM
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Cho tam giác ABC không tù . CMR : tanA2 + tanB2+tanC2 + tanA2tanB2tanC2 ≥ 10√39
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Cho sinα+sinβ+sinγsin(α+β+γ)=cosα+cosβ+cosγcos(α+β+γ)=mTìm min với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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Cho \frac{\sin \alpha+\sin \beta+\sin \gamma }{\sin(\alpha+\beta+\gamma)}=\frac{\cos\alpha+\cos\beta+\cos\gamma}{\cos(\alpha+\beta+\gamma)}=mTìm \min P=\cos^n(\alpha+\beta)+cos^n(\beta+\gamma)+cos^n(\gamma+\alpha) với n\in Z;n\ge2
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CHứng minh rằng sinx+siny+sinz \leq 3.sin \frac{x+y+z}{3}
Trả lời 04-05-16 08:55 PM
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cho tam giác ABC thỏa mãn:\frac{1}{\sin ^{a}A}+\frac{1}{\sin ^{b}B}+\frac{1}{\sin ^{c}C}\leq \frac{1}{\sqrt[x]{\cos \frac{A}{2}}}+\frac{1}{\sqrt[y]{\cos \frac{B}{2}}}+\frac{1}{\sqrt[z]{\cos \frac{C}{2}}} (với $a, b, c, x, y,z \in...
Trả lời 02-05-16 12:18 PM
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Chứng minh \frac 1{\sin A}+\frac 1{\sin B}+\frac 1{\sin C} \ge \frac{1}{\cos \frac A2}+\frac 1{\cos \frac B2}+\frac 1{\cos \frac C2}
Trả lời 02-05-16 11:55 AM
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tam giác ABC sẽ có đặc điểm gì nếu....:\frac{\sqrt[2016]{\sin A }+\sqrt[2016]{\sin B}+\sqrt[2016]{\sin C}}{\sqrt[2016]{\cos \frac{A}{2}}+\sqrt[2016]{\cos \frac{B}{2}}+\sqrt[2016]{\cos \frac{C}{2}}}=1......................................................................
Trả lời 30-04-16 12:34 PM
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giải pt lượng giác:\frac{4sin^{2}2a}{1-cos^{2}a}=2
Trả lời 13-04-16 08:29 PM
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CMR:m_{a}.m_{b}.m_{c}\geq l_{a}.l_{b}.l_{c}
Trả lời 10-04-16 10:51 PM
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\cos (\sin x) >\sin (\cos x)
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a) \cos A+\cos B+ \cos C \le \frac 32b) \cos2A+\cos 2B+\cos 2C \ge \frac{-3}2c)\sin \frac A2+\sin \frac B2+\sin \frac C2 \le \frac 32d) \cos A-\cos B + \cos C \ge \frac{-3}2
Trả lời 27-01-16 10:55 PM
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a) \cos A+\cos B+ \cos C \le \frac 32b) \cos2A+\cos 2B+\cos 2C \ge \frac{-3}2c)\sin \frac A2+\sin \frac B2+\sin \frac C2 \le \frac 32d) \cos A-\cos B + \cos C \ge \frac{-3}2
Trả lời 26-01-16 10:44 PM
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