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# Trig Functions C3 watch

1. Could someone help me out with this

4cos2ϴ+sec2 ϴ =5

where 0<ϴ<360

I have tried everything but I keep cancelling out the sin or cos,the answer in the book is:

ϴ=0,180,360,60,120,240,300

PS. please don't just give full solution could you just give pointers, thanks!
2. Make sec in to 1/cos
3. (Original post by Dabo_26)
Could someone help me out with this

4cos2ϴ+sec2 ϴ =5

where 0<ϴ<360

I have tried everything but I keep cancelling out the sin or cos,the answer in the book is:

ϴ=0,180,360,60,120,240,300

PS. please don't just give full solution could you just give pointers, thanks!
Use the identity for secx which is 1/cosx and times everything by cosx and you should get a quartic equation, which you can factorise.

Hint: use substition of Y = (cosx)^2
4. (Original post by kkboyk)
Use the identity for secx which is 1/cosx and times everything by cosx and you should get a quartic equation, which you can factorise.

Hint: use substition of Y = (cosx)^2
yeh, did it thanks
5. (Original post by Dabo_26)
yeh, did it thanks
No problem

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