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Calculator inverse tangent problem 
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#1
Feb907, 08:54 PM

P: 44

1. The problem statement, all variables and given/known data
Suppose that a wind is blowing from the direction N45ºW at a speed of 50 km/h. A pilot is steering a plane in the direction N60ºE at an airspeed of 250 km/h. Find the true course (direction) and ground speed (magnitude) of the plane. 2. Relevant equations 3. The attempt at a solution The resultant vector will be in an upward direction in the second quadrant, right? I determined that the resultant vector v = <25(√2)  125(√3), 25(√2) + 125> I am trying to find the angle that the plane is flying. tan θ = [25(√2) + 125]/[25(√2)  125(√3)] Using inverse tangent and my calculator, I got an angle around 41.5 degrees. If the resultant vector is in the second quadrant, this is wrong. I remember that the calculator sometimes will not work for inverse tangent, but I can't remember when, or what to do to fix it. Please help. 


#2
Feb907, 09:20 PM

Mentor
P: 15,201

Use your trig identities. What is [itex]\tan(\theta+180^\circ)[/itex]?



#3
Feb907, 09:29 PM

P: 44

The same thing...I was thinking I had to add something. I couldn't remember what though. Thanks



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