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\(a,A=\dfrac{3x+2-3x+2+3x-6}{\left(3x-2\right)\left(3x+2\right)}=\dfrac{3x-2}{\left(3x-2\right)\left(3x+2\right)}=\dfrac{1}{3x+2}\\ b,B=\dfrac{1}{2}+\dfrac{x}{\dfrac{x+2-x}{x+2}}=\dfrac{1}{2}+\dfrac{x}{\dfrac{2}{x+2}}=\dfrac{1}{2}+\dfrac{x\left(x+2\right)}{2}\\ B=\dfrac{1+x^2+2x}{2}=\dfrac{\left(x+1\right)^2}{2}\)
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Vì 75 ° + 15 ° = 90 ° nên sin 75 ° = cos 15 °
Vì 53 ° + 37 ° = 90 ° nên cos 53 ° = sin 37 °
Vì 47 ° 20 ' + 42 ° 40 ' = 90 ° nên sin 47 ° 20 ' = cos 42 ° 40 '
Vì 62 ° + 28 ° = 90 ° nên tg 62 ° = cotg 28 °
Vì 82 ° 45 ' + 7 ° 15 ' = 90 ° nên cotg 82 ° 45 ' = tg 7 ° 15 '
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\(\sqrt{41+12\sqrt{5}}=\sqrt{\left(6+\sqrt{5}\right)^2}=6+\sqrt{5}\)
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a) \(\sqrt{28+10\sqrt{3}}=\sqrt{\left(5+\sqrt{3}\right)^2}=\left|5+\sqrt{3}\right|=5+\sqrt{3}\)
b) \(\sqrt{7+3\sqrt{5}}=\sqrt{\left(\dfrac{3\sqrt{2}}{2}+\dfrac{\sqrt{10}}{2}\right)^2}=\dfrac{3\sqrt{2}}{2}+\dfrac{\sqrt{10}}{2}\)
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sin 55độ=cos 35độ
cos 63độ=sin 27độ
sin 80độ 15p=cos 9độ 45p
tan 87độ=cotg 3độ
cotg 82độ 43p= tan 7độ 17p