The Student Room Group

Polar co ordinates; finding area

question6.PNG

(I guessed 3pi) Does this make sense without the range given?
Reply 1
Avatar for Pangol
Pangol
15
Original post by ckfeister
question6.PNG

(I guessed 3pi) Does this make sense without the range given?


If no range is given, you can presume that they mean that all values of theta are acceptable, that it, from 0 to 2pi (or -pi to pi, whichever convention you are using). It really helps if you can come up with a basic sketch, as there are often symmetry ideas that can save you a lot of time.
Original post by ckfeister
question6.PNG

(I guessed 3pi) Does this make sense without the range given?


Yes because if you sketch it, it's an enclosed shape on it's natural domain so the area would be bounded by it entirely on [−π,π)[-\pi,\pi)
Reply 3
Avatar for ckfeister
ckfeister
OP
19
Original post by Pangol
If no range is given, you can presume that they mean that all values of theta are acceptable, that it, from 0 to 2pi (or -pi to pi, whichever convention you are using). It really helps if you can come up with a basic sketch, as there are often symmetry ideas that can save you a lot of time.


Original post by RDKGames
Yes because if you sketch it, it's an enclosed shape on it's natural domain so the area would be bounded by it entirely on [−π,π)[-\pi,\pi)


Where did I do a stupid mistake?

answer6.jpg
Original post by ckfeister
Where did I do a stupid mistake?

answer6.jpg


cos (-pi) = -1, same as cos pi not - cos pi

So these two terms cancel out.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you