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# Two people start from the same point. One walks east at $3 mi/h$ and the other walks northeast at $2 mi/h.$ How fast is the distance between the people changing after 15 minutes?

## $\frac{d a}{d t}=\sqrt{13-6 \sqrt{2}} \approx 2.125[$ miles per hour $]$

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### Video Transcript

to figure out how fast the distance is changing. We know we can use the loft. Co signs, which is a squared, is B squared plus C squared minus two b c. Co sign data, which is 45 degrees, which gives us a jazz square of B squared plus C squared, minus specie squared to use unit. Second, figure out what co signed a 45 degrees is which gives us d A over DT so you can plug this end So we have 1/2 thes squared plus C squared minus sort of two BC to the negative 1/2 and you multiply it by two b d B over G onwards, and you end up with 2.1 to 5 miles per hour.

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