How do I deal with parametric equations? x = 4 cos ( t + pi/6), y = 2 sin t, Show that x + y = 2sqrt(3) cos t.
Note: I have a screenshot of the question that I should be able to add to the work space. Q5 C4 June 2014 Edexcel.x + y = 2sqrt(3) cos tStart with x = 4 cos ( t + pi/6) and the trig identity cos(A + B) = cosAcosB - sinAsinBx = 4(cos(t)cos(pi/6) - sin(t)sin(pi/6))Ideally you should be able to recognise cos(pi/6) = sqrt(3)/2 and sin(pi/6)=1/2, but your calculator should give you this in surd form where appropriate, although you can try dividing answers by sqrt(2) and sqrt(3).x= 4((sqrt(3)/2)*cos(t) - sin(t)/2) = 2sqrt(3)*cos(t) - 2 sin(t)Notice the latter is y.x = 2sqrt(3)*cos(t) - y. Therefore x + y = 2sqrt(3).
KD
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