Obliczenia :
[tex]\cos\alpha=\frac{2}{3}\\\\\sin^2\alpha+\cos^2\alpha=1\\\\\sin^2\alpha+(\frac{2}{3})^2=1\\\\\sin^2\alpha+\frac{4}{9}=1 \ \ |-\frac{4}{9}\\\\\sin^2\alpha=\frac{5}{9}\\\\3\sin^2\alpha-5=3\cdot\frac{5}{9}-3=\frac{5}{3}-3=-1\frac{1}{3}[/tex]
Odp. 3sin²α - 5 = -1 ¹/₃.
