Friday

April 25, 2014

April 25, 2014

Posted by **bryan** on Sunday, February 3, 2013 at 1:29pm.

- Calculus -
**Steve**, Sunday, February 3, 2013 at 2:03pmone way, using the law of cosines. Draw a triangle. The angle between the two journeys is 45°. At time t, the distances traveled are 3t and 2t. So, the distance x is

x^2 = (3t)^2 + (2t)^2 - 2(3t)(2t)*1/√2

x^2 = 9t^2 + 4t^2 - 6√2 t^2

x^2 = (13-6√2)t^2

At t=15, x = 15√(13-6√2)

2x dx/dt = 2(13-6√2)t

2*15√(13-6√2) dx/dt = 30(13-6√2)

dx/dt = √(13-6√2)

using vectors,

x = (3t,0) - (√2t,√2t) = ((3-√2)t,√2t)

dx/dt = (3√2,-√2)

|dx/dt|^2 = (3-√2)^2 + √2^2 = 9-6√2+2+2 = 13-6√2

|dx|dt| = √(13-6√2)

**Related Questions**

calculus - Two people start from the same point. One walks east at 3 mi/h and ...

calculus - A piece of land is shaped like a right triangle. Two people start at ...

Related rates - Two people start from the same point. One walks east at 1 mi/h ...

math - Two runners start moving from the same point A on a circular track but in...

calculus - Two cars start moving from the same point. One travels south at 28mi/...

calculus - Two cars start from the same point at the same time. One travels ...

physics - An Atwood machine consists of two masses (m1 = 175 grams, m2 = 485 ...

physics - Two identical +9.5uF point charges are initially 3.5cm from each other...

physics - two student walk in the same direction along a straight path, at a ...

calculus - Could someone help me et up this problem? Two people start from the ...