Posted by **Adrianna** on Saturday, March 17, 2012 at 9:29pm.

Two airplanes take off from an airport at the same time. One travels on a heading of 45 at 420 mph and the other on a heading of 150 at 400 mph. After two hours, how far apart are the airplanes?

A.650.66 miles

B.1,160 miles

C.1,301 miles

- Pre-Cal -
**Reiny**, Saturday, March 17, 2012 at 9:48pm
Use the cosine law, I got 650.66

- Pre-Cal -
**Adrianna**, Saturday, March 17, 2012 at 9:51pm
Can you tell me how you did it? I got 5 more questions like this one.

- Pre-Cal -
**Reiny**, Saturday, March 17, 2012 at 9:53pm
are you not familar with the cosine law?

You must have learned this to be able to do this kind of question.

- Pre-Cal -
**Adrianna**, Saturday, March 17, 2012 at 9:58pm
Yes I am, but I don't understand it. I don't have a teacher to teach me. I do my work online, and I just need 2nd semester of pre-cal to graduate.

- Pre-Cal -
**Reiny**, Saturday, March 17, 2012 at 10:02pm
x^2 = 420^2 + 400^2 - 2(420)(400)cos 105°

do the arithmetic

I got 105° from the difference between 150° and 45°

- Pre-Cal -
**Adrianna**, Saturday, March 17, 2012 at 10:07pm
thanks

- Pre-Cal -
**Henry**, Wednesday, April 15, 2015 at 10:59pm
d1 = 420mi/h[45o] * 2h = 840mi[45o]

d2 = 400mi/h[150o] * 2h = 800mi[150o]

D = 840[45o] - 800[150o]

X = 840*Cos45 - 800*cos150 = 1287 mi

Y = 840*sin45 - 800*sin150 = 194 mi

D = sqrt(1287^2+194^2) = 1301.5 mi

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