polar coordinates doubtWatch

#1
This is a doubt from example 12 of the edexcel fp2 textbook if you have it.

My doubt is that in part a the answer that they get is r=4a/3 square root of 3 cosec theta
but shouldn't the answer be r=4a/3 root 3 cosec (theta - pi/2)?
As the it makes 90 degrees with the y-axis? If not, then what exactly is that angle value, how is it found? And how do we decide when to use cosec and when to use sec?
0
7 years ago
#2
(Original post by mintmocha)
...
Looking at the attached diagram, theta is the angle between the radial and the postive "x-axis".

So r sin(theta) = y

and hence r = y cosec(theta)
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