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# P3 help watch

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1. I'm rather stuck on this question.

given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

*******************************

I started by doing:

cosec C = 7

1/(sin C) = 7

(1/7) = sin C

But then got stuck about here.
2. (Original post by 2776)
I'm rather stuck on this question.

given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

*******************************

I started by doing:

cosec C = 7

1/(sin C) = 7

(1/7) = sin C

But then got stuck about here.
Poor 2776, nobody has helped him on his maths question yet.
3. Do you do edexcel p3? not seen anything like that before sorry.
4. (Original post by Absolution)
Do you do edexcel p3? not seen anything like that before sorry.
OCR
5. (Original post by 2776)
OCR
ah that would explain it, i haven't covered that sort of equation before and hopefully won't have too good luck !
6. 1 + cot^2 = cosec^2, so
cot^2 C = 48 etc
7. (Original post by 2776)
I'm rather stuck on this question.

given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

*******************************

I started by doing:

cosec C = 7

1/(sin C) = 7

(1/7) = sin C

But then got stuck about here.
i got cot C=sqrt(48),sec D=sqrt(2) and -sqrt(2),cosec E=sqrt(5)/2.
There are more asumming postive and negative roots,also wot are the domains of the angles C, D, E?
8. (Original post by IntegralAnomaly)
i got cot C=sqrt(48),sec D=sqrt(2) and -sqrt(2),cosec E=sqrt(5)/2.
There are more asumming postive and negative roots,also wot are the domains of the angles C, D, E?
No domains mentioned. I think it is only wanting to ask for the first few answers. Cheers, got it now.
9. (Original post by 2776)
I'm rather stuck on this question.

given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.
cosec C = 7

squaring gives:

cosec^2 C = 49

using identity gives:

1 + cot^2 C = 49

rearranging gives:

cot^2 C = 48

square rooting gives:

cot C = plus or minus √48 = plus or minus 4√3

sin^2 D = 0.5

using identity gives:

1 - cos^2 D = 0.5

rearranging gives:

cos^2 D = 0.5

square rooting gives

cos D = plus or minus 1/√2

taking reciprocal:

sec D = plus or minus √2

I'll have to think about the third one.
10. its really the E one taht I'm stuck on, tried sec²E = 5, then sin²E/cos²E = 4, but not really going anywhere.
11. (Original post by hornblower)
cosec C = 7

squaring gives:

cosec^2 C = 49

using identity gives:

1 + cot^2 C = 49

rearranging gives:

cot^2 C = 48

square rooting gives:

cot C = plus or minus √48 = plus or minus 4√3

sin^2 D = 0.5

using identity gives:

1 - cos^2 D = 0.5

rearranging gives:

cos^2 D = 0.5

square rooting gives

cos D = plus or minus 1/√2

taking reciprocal:

sec D = plus or minus √2

I'll have to think about the third one.
for the third 1 tanE=2(im nt taking the negative 1)
therefore sinE=2/(sqrt(5)) (using a right angled triangle with angle E)
ergo cosec E =sqrt(5)/2
12. (Original post by 2776)
I'm rather stuck on this question.

given that cosec C = 7, sin²D = 0.5 and tan²E = 4, find the possible values of cot C, sec D and cosec E, giving your answers in exact form.

*******************************

I started by doing:

cosec C = 7

1/(sin C) = 7

(1/7) = sin C

But then got stuck about here.
For cosec(E), if you take the reciprocal of tan^2(E) to find cot^2(E) = 1/4, then use the identity;

cosec^2(E) = 1 + cot^2(E)

So cosec^2(E) = 5/4 and cosec(E) = (sqrt5)/2, as the person above correctly stated.

Ben
13. (Original post by Ben.S.)
For cosec(E), if you take the reciprocal of tan^2(E) to find cot^2(E) = 1/4, then use the identity;

cosec^2(E) = 1 + cot^2(E)

So cosec^2(E) = 5/4 and cosec(E) = (sqrt5)/2, as the person above correctly stated.

Ben
oh yes thats a much better way

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