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 June 5th, 2019, 02:09 PM #1 Member   Joined: Jan 2019 From: tornto Posts: 48 Thanks: 0 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.
June 5th, 2019, 02:33 PM   #2
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Quote:
 Originally Posted by yorkmanz 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 ...

$|QR| = \sqrt{|PQ|^2+|PR|^2 - 2|PQ| \cdot |PR| \cdot \cos(142^\circ)}$

Last edited by skipjack; June 5th, 2019 at 09:02 PM.

 June 6th, 2019, 02:59 PM #3 Member   Joined: Jan 2019 From: tornto Posts: 48 Thanks: 0 my answer is 7.430102967 correct? thanks
June 6th, 2019, 03:15 PM   #4
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Quote:
 Originally Posted by yorkmanz my answer is 7.430102967 correct? thanks
no ... also, the directions say two decimal places
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