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x∈(0 grade,9 grade)
cos²x(1+ctg²x) supra ctg²x= Konstant


Răspuns :

[tex] [cos^{2} x(1 + \frac{ cos^{2}x }{ sin^{2}x } )] / [ \frac{ cos^{2}x }{ sin^{2}x } ] \\ = [ cos^{2}x( 1 + \frac{ cos^{2}x }{ sin^{2}x })][ \frac{ sin^{2}x }{ cos^{2}x } ] \\ = sin^{2} x + cos^{2}x = 1 [/tex]