Odpowiedź:
[tex]sin^{2} 20 + tg^{2} 30 + sin^{2} 70 = sin^{2} 20 + sin^{2}(90-20) + tg^{2} 30 = sin^{2} 20 + cos^{2} 20 + tg^{2} 30 = 1 + tg^{2} 30 = 1 + (\frac{\sqrt{3} }{3} )^{2} = 1 + \frac{3}{9} = 1+ \frac{1}{3}= \frac{4}{3}[/tex]
cos125-cos55= -2[tex]sin \frac{125 + 55}{2} sin \frac{125 - 55}{2} = -2sin90sin35 = -2 * 1*sin35= -2sin35[/tex]