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Solving Trig Equations

does anybody know how to solve this :

root 2 cos ( x + 1/4 pie) =1

because i keep getting the wrong answer
does anybody know how to go about it?
Reply 1
Avatar for Swayum
Swayum
18
Well, what are you doing that goes wrong? I'd start by saying let u = x + pi/4, so that what you're trying to solve is root2 cos(u) = 1, which feels easier. Solve that for u and hence for x.

It's pi, by the way, not "pie" :lolwut:
(edited 13 years ago)
the answer is 0, 3/2pie, 2pi :/

i don't know where 2 pi comes from!
Hi OP, can we please know the range of values for which we are solving x? ie. -2pi<x<2pi or what have you. I had a long explanation written out ready to post but I closed my browser by accident lol. It was probably too long to read anyway (though I do like to explain the whole thing if I attempt to explain something, so the OP understands more in general x.x)
(edited 13 years ago)
yeah sorry it is 0< a < pi/2
one of the answers is 2pi but i dont know where that comes from!
Did you get any of the answers?
(edited 13 years ago)
yeah i got the others! not that one though
i've got another question which i can't do aswell!
Yeah, there are only 2 answers for this. 2pi is not a solution of x in this interval.
do you think the answer in the back is wrong then?
Yep.
oh no that's part a of the question
part bs range is 0x2pi

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