Răspuns:
Dupa formula fundamentala a trigonometriei:
[tex]sin^2x+cos^2x=1[/tex], ∀x∈R
[tex]a) sin^230+cos^230=1[/tex]
[tex]tg(30)*ctg(30)=\frac{1}{ctg(30)}*ctg(30)=1[/tex]
[tex]b)sin^245+cos^245=1\\tg45*ctg45=1\\c)sin^260+cos^260=1\\tg60*ctg60=1[/tex]
