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Mathematics
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OpenStudy (anonymous):
d
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OpenStudy (amistre64):
its just a quadratic in disguise
OpenStudy (anonymous):
\[14\sin X \cos X-14\sin X=-7,2\sin X \cos X=-1+2\sin X\]
Squaring both sides,
\[4\sin ^{2}x \cos ^{2}x=1+4\sin ^{2}x-4\sin x\]
\[4\sin ^{2}x \left( 1-\sin ^{2}x \right)-1-4\sin ^{2}x+4\sin x=0\]
\[-4\sin ^{4}x+4\sin x-1=0\]
OpenStudy (amistre64):
let u = sin(x)
7u^2 - 14u + 2 = -5
OpenStudy (anonymous):
is it sin2x orsin ^2 x
OpenStudy (amistre64):
:)
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OpenStudy (anonymous):
so the answer is zero?
OpenStudy (amistre64):
what is the solution of:
7u^2 - 14u + 2 = -5
OpenStudy (jdoe0001):
\(\bf 7 sin^2(x) - 14 sin(x) + 2 = -5 \implies 7 sin^2(x) - 14 sin(x) + 7 = 0\\
7[sin^2(x) - 2sin(x) + 1] = 0\\
\textit{let sin(x) = u as amistre64 said}\\
7[x^2-2x+1] = 0\)
OpenStudy (amistre64):
7u^2 - 14u + 2 = -5
7u^2 - 14u + 7 = 0
u^2 - 2u + 1 = 0
(u-1)^2 = 0
OpenStudy (jdoe0001):
woops, made x instead of u, anyhow hhehe
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OpenStudy (amistre64):
let sin(x) = chi :)
OpenStudy (jdoe0001):
chi chi chia
OpenStudy (jdoe0001):
kiimiilee then just solve the quadratic for "u" or sin(x)
OpenStudy (amistre64):
"all" solutions will require you to period the both angles by multiples of 2pi
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