Odpowiedź :
[tex]sin^2\alpha+cos^2\alpha=1 \\tg\alpha=\frac{sin\alpha}{cos\alpha}\\\\\frac{1-sin^2\beta}{1-cos^2\beta}*tg^2\beta=\frac{cos^2\beta}{sin^2\beta}*(\frac{sin\beta}{cos\beta})^2=\frac{cos^2\beta}{sin^2\beta}*\frac{sin^2\beta}{cos^2\beta}=1[/tex]