# Calculator inverse tangent problem

by merced
Tags: calculator, inverse, tangent
 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.
 Mentor P: 13,650 Use your trig identities. What is $\tan(\theta+180^\circ)$?
 P: 44 The same thing...I was thinking I had to add something. I couldn't remember what though. Thanks

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