Suppose that $u_1$ and $u_2$ are orthogonal vectors, with $||u_1|| = 2$
and $||u_2|| = 5$. Find $||3u_1 + 4u_2||$
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Then, $u_1 \cdot u_1 = 4$ and $u_2\cdot u_2 = 25$. And $||3u_1 + 4u_2|| = \sqrt{(3u_1 + 4u_2)\cdot(3u_1 + 4u_2)}$ But the thing is I don't know what to do with this information. Any help?
[Math] Length of Orthogonal Vectors
linear algebra
Best Answer
Hint: If $u_1, u_2$ are orthogonal, then their dot product is zero.
Can you take it from there?