Lösung 4.3:4d
Aus Online Mathematik Brückenkurs 1
(Unterschied zwischen Versionen)
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- | {{ | + | With the formula for double angles and the Pythagorean identity |
- | < | + | <math>\cos ^{2}v+\sin ^{2}v=1</math>, we can express |
- | {{ | + | <math>\text{cos 2}v\text{ }</math> |
+ | in terms of | ||
+ | <math>\text{cos }v</math>, | ||
+ | |||
+ | |||
+ | <math>\begin{align} | ||
+ | & \text{cos 2}v=\cos ^{2}v-\sin ^{2}v=\cos ^{2}v-\left( 1-\cos ^{2}v \right) \\ | ||
+ | & =2\cos ^{2}v-1=2b^{2}-1 \\ | ||
+ | \end{align}</math> |
Version vom 11:48, 29. Sep. 2008
With the formula for double angles and the Pythagorean identity \displaystyle \cos ^{2}v+\sin ^{2}v=1, we can express \displaystyle \text{cos 2}v\text{ } in terms of \displaystyle \text{cos }v,
\displaystyle \begin{align}
& \text{cos 2}v=\cos ^{2}v-\sin ^{2}v=\cos ^{2}v-\left( 1-\cos ^{2}v \right) \\
& =2\cos ^{2}v-1=2b^{2}-1 \\
\end{align}