Solve the equation on the interval [0, 2π).
sin2 x - cos2 x = 0
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OpenStudy (anonymous):
sry no lol
OpenStudy (anonymous):
and you should convince yourself why it is fine to divide by cos2x . ( it is fine. )
OpenStudy (anonymous):
wud it b pie/4, pie/6
?
OpenStudy (anonymous):
wait im stupid
OpenStudy (anonymous):
tan(2x) = 1 !!
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OpenStudy (anonymous):
??
OpenStudy (anonymous):
so the general solution for
tan(x) = tan(y)
x = y + pi*k
so in our case:
tan(2x) = tan(pi/4)
2x = pi/4 + pi*k
x = pi/8 + (pi/2) * k
OpenStudy (anonymous):
pie/4 just then
OpenStudy (anonymous):
no
OpenStudy (anonymous):
u got over 8?
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OpenStudy (anonymous):
pi/8 , 5pi/8 , 9pi/8 , 13pi/8
OpenStudy (anonymous):
i first wrote tan(2x) = 0 which was WRONG
OpenStudy (anonymous):
pi/4, 3pi/4, 5pi/4, 7pi/4
OpenStudy (anonymous):
no,
x=pi/8 , 5pi/8 , 9pi/8 , 13pi/8
OpenStudy (anonymous):
hmm
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OpenStudy (anonymous):
wait lol
was it :
OpenStudy (anonymous):
\[\sin(2x) - \cos(2x) = 0\]
OpenStudy (anonymous):
or
\[\sin^2(x) - \cos^2(x) = 0\]
OpenStudy (anonymous):
cause i solved for the FIRST one
OpenStudy (anonymous):
?
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OpenStudy (anonymous):
it said i got it right for the four i picked? weird
OpenStudy (anonymous):
but what was the correct question
i wrote here two
OpenStudy (anonymous):
i think i solved for the wrong one
OpenStudy (anonymous):
im lost sry its ok bc i got it right so its all good :)
OpenStudy (anonymous):
cause if the question was :
sin^2(x) - cos^2(x) = 0
then we get
tan^2(x) = 1
tan(x) = +/-1
so
1. tan(x) = 1
tan(x) = tan(pi/4)
x = pi/4 + pi * k
x = pi/4 , 5pi/4
2.tan(x) = -1
tan(x) = tan(-pi/4)
x = -pi/4 + pi*k
x = 3pi/4 , 7pi/4
so : x = pi/4, 3pi/4, 5pi/4, 7pi/4
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