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June 5th, 2019, 02:09 PM   #1
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Three ships

Three ships are at points P, Q, and R such that PQ = 2km, PR = 7km, and $\small\angle$QPR = 142$^\circ\!$.
What is the distance between Q and R, to two decimal places?

Please help.

Last edited by skipjack; June 5th, 2019 at 09:02 PM.
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June 5th, 2019, 02:33 PM   #2
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Originally Posted by yorkmanz View Post
Three ships are at points P, Q, and R such that PQ = 2km, PR = 7km, and $\small\angle$QPR = 142$^\circ\!$.
What is the distance between Q and R, to two decimal places?

Please help.
Use the law of cosines ...

$|QR| = \sqrt{|PQ|^2+|PR|^2 - 2|PQ| \cdot |PR| \cdot \cos(142^\circ)}$
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Last edited by skipjack; June 5th, 2019 at 09:02 PM.
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June 6th, 2019, 02:59 PM   #3
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my answer is
7.430102967 correct?
thanks
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June 6th, 2019, 03:15 PM   #4
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Originally Posted by yorkmanz View Post
my answer is
7.430102967 correct?
thanks
no ... also, the directions say two decimal places
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