solve sin² theta - cos theta = 1 by 4 for theta and write values of theta in interval 0< theta<2π
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Answered by
7
sin^2 theta - cos theta=1/4
=>1-cos^2 theta-cos theta=1/4
=>cos^2theta - cos theta -3/4=0
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by formula
x=[-b±√b^2-4ac]/2a
cos theta=[-1±√{1-+4(1)(3/4)}]/2
cos theta =[-1±√(1+3)]/2
cos theta=(-1±2)/2
cos theta =1/2,-3/2
but -1≤cos theta≤1
so cos theta=1/2
or
cos theta=cos(π/3) or cos 4π/3
as theta belongs to 0 to 2π
theta =π/3,4π/3
=>1-cos^2 theta-cos theta=1/4
=>cos^2theta - cos theta -3/4=0
_________________________
------------
by formula
x=[-b±√b^2-4ac]/2a
cos theta=[-1±√{1-+4(1)(3/4)}]/2
cos theta =[-1±√(1+3)]/2
cos theta=(-1±2)/2
cos theta =1/2,-3/2
but -1≤cos theta≤1
so cos theta=1/2
or
cos theta=cos(π/3) or cos 4π/3
as theta belongs to 0 to 2π
theta =π/3,4π/3
Answered by
6
π/3
4π/3
these are the answers
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4π/3
these are the answers
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