Uzasadnij toższamość 2

arekarekarek · Post autor: **arekarekarek** » 18 mar 2009, o 13:20

\(\displaystyle{ \frac{2}{cos^2 \alpha } - ( tg \alpha + ctg \alpha ) ^2 = tg^2 \alpha - ctg^2 \alpha}\)

Potekk · Post autor: **Potekk** » 18 mar 2009, o 14:32

\(\displaystyle{ \frac{2}{cos^2 \alpha } - ( tg \alpha + ctg \alpha ) ^2 = \frac{2\sin^2 \alpha +2\cos^2 \alpha }{\cos^2 \alpha }- \tg^2 \alpha -2\tg \alpha \ctg \alpha - \ctg^2 \alpha =2\tg^2 \alpha +2-\tg^2 \alpha -2 -\ctg^2 \alpha =tg^2 \alpha - ctg^2 \alpha}\)

arekarekarek · Post autor: **arekarekarek** » 18 mar 2009, o 14:41

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