If $ | \vec{a} | = 3 $, $ | \vec{b} | = 2 $, then find $ (3\vec{a} - 2\vec{b}) \cdot (3\vec{a} + 2\vec{b}) $.
The value of $ i^3 + i^4 + i^5 $+ .. + $i^{93}$ is:
If $ |\vec{a}| = 5 $, $ |\vec{b}| = 8 $, $ |\vec{a} - \vec{b}| = 7 $, find the angle between $ \vec{a} $ and $ \vec{b} $.
In a GP 9, 3, $ \frac{1}{3} $, $ \frac{1}{9} $, … find the 25th term.