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Calculati ctg a,stiind ca sin a =1 supra 3 si a∈(0 si pi supra 2).[tex] [/tex]

Răspuns :

[tex]\it ctg a =\dfrac{cos a}{sin a} =\dfrac{\sqrt{1-sin^2 a}}{sin a}=\dfrac{\sqrt{1-\dfrac{1}{9}}}{\dfrac{1}{3}}=\dfrac{\sqrt{\dfrac{8}{9}}}{\dfrac{1}{3}} =\dfrac{\dfrac{2\sqrt2}{3}}{\dfrac{1}{3}} =2\sqrt2[/tex]
sqrt= radical, sqr= la patrat:
ctg a= (cos a)/(sin a), cos a=sqrt(1-sqr(sin(a)), cos a= sqrt(1-1/9)= 2*sqrt(2)/3=>
ctg a= (2*sqrt(2)/3)/(1/3)= 2*sqrt(2).