Zad. 4
tg\alpha=\frac{1}{3}
\frac{sin\alpha}{cos\alpha}=\frac{1}{3}
cos\alpha=3sin\alpha
sin^2\alpha+cos^2\alpha=1
sin^2\alpha+9sin^2\alpha=1
10sin^2\alpha=1
sin\alpha=\sqrt{\frac{1}{10}}=\frac{1}{\sqrt{10}} *\frac{\sqrt{10}}{\sqrt{10}}=
=\frac{\sqrt{10}}{10}
cos\alpha=3*\frac{\sqrt{10}}{10}=\frac{3\sqrt{10}}{10}
sin\alpha*cos\alpha=\frac{\sqrt{10}}{10}*\frac{3\sqrt{10}}{10}
Odp. c
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