HOC24
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\(\frac{sin2a-c\text{os}2a}{sin2a-c\text{os}2a}=tan4a-\frac{1}{c\text{os}4a}\)
\(c\text{os}3a=4cosa.c\text{os}\left(\frac{\pi}{3}-a\right).c\text{os}\left(\frac{\pi}{3}+a\right)\)
\(2cos\left(\frac{\pi}{4}+x\right)cos\left(\frac{\pi}{4}-x\right)=c\text{os}2x\)
\(cot2a+\frac{1}{sin2a}=cota\)
\(c\text{os}^2a+2sin^22a\)
\(\frac{x}{x+2}+4>-5\sqrt{\frac{x+2}{x}}\)
\(sin^4x+c\text{os}^4x=\frac{3}{4}+\frac{1}{4}c\text{os}4x\)
\(\left(x+1\right)\left(\sqrt{2-x}+2-x\right)\le0\)