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A Level Maths Trig

How would you do part aii of this question? I understand that you're somehow meant to use the previous part, but I'm not sure how. Screenshot 2023-05-31 at 16.30.42.jpg
Reply 1
You know know exact values for sin(pi/6) and sin(pi/4)?
Reply 2
Original post by mqb2766
You know know exact values for sin(pi/6) and sin(pi/4)?


Sorry, I still don't quite understand.
Reply 3
Original post by cloudii
Sorry, I still don't quite understand.


Just have a bit of a think, but there are two values for tan/cot in the question pi/12 and pi/8. Have a think how they can be used in the first part and think about which angles you know trig values for.
Reply 4
Original post by mqb2766
Just have a bit of a think, but there are two values for tan/cot in the question pi/12 and pi/8. Have a think how they can be used in the first part and think about which angles you know trig values for.

Oh, I'm being an idiot, can you rearrange the first part so that you get tan theta + cot theta = 2/ (sin2theta), group together (tan pi/12 + cot pi/12) + (tan pi/8 + cot pi/8), hence theta is pi/12 and pi/8, and then sub that back in so that the answer is 2/(sin 2 x pi/2) + 2/(sin 2 x pi/8)?
Reply 5
Original post by cloudii
Oh, I'm being an idiot, can you rearrange the first part so that you get tan theta + cot theta = 2/ (sin2theta), group together (tan pi/12 + cot pi/12) + (tan pi/8 + cot pi/8), hence theta is pi/12 and pi/8, and then sub that back in so that the answer is 2/(sin 2 x pi/2) + 2/(sin 2 x pi/8)?


Sounds about right (approach). Its just a bit of pattern spotting, so thinking about what the question tells you and what you know.
(edited 12 months ago)

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