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Mathematics 21 Online
OpenStudy (maheshmeghwal9):

Please Solve:-

OpenStudy (maheshmeghwal9):

\[\cos^{-1} (x)-\sin^{-1} (x)=0\]

OpenStudy (maheshmeghwal9):

Please solve for "x" :)

OpenStudy (maheshmeghwal9):

I have done as this:- \[\cos^{-1} (x)-\sin^{-1} (x)+\sin^{-1} (x)=\sin^{-1} (x).\] \[\pi/2 = 2\sin^{-1} (x).\]

OpenStudy (asnaseer):

you can represent this in the following right angled triangle: |dw:1338216489833:dw|

OpenStudy (asnaseer):

here:\[\cos(\theta)=\sin(\theta)=\frac{x}{1}=1\]so what is \(\theta\)?

OpenStudy (asnaseer):

sorry - that should be an x at the right hand side

OpenStudy (asnaseer):

\[\cos(\theta)=\sin(\theta)=\frac{x}{1}=x\]

OpenStudy (maheshmeghwal9):

\[\sin^{-1} (x)\] or \[\cos^{-1} (x)\]

OpenStudy (asnaseer):

the equations I wrote can be rewritten as:\[\theta=\cos^{-1}(x)=\sin^{-1}(x)\]

OpenStudy (maheshmeghwal9):

so theta should be pi/4

OpenStudy (asnaseer):

yes

OpenStudy (maheshmeghwal9):

& we get x=1/sqrt(2)

OpenStudy (asnaseer):

yes

OpenStudy (maheshmeghwal9):

but in my method I am getting 2 values for "x".\[(1/\sqrt{2}) ;-(1/\sqrt{2})\]

OpenStudy (maheshmeghwal9):

my method is stated above. please help:)

OpenStudy (asnaseer):

how did you get to:\[\pi/2 = 2\sin^{-1} (x)\]

OpenStudy (maheshmeghwal9):

since in my course ; we state a property as:-\[\sin^{-1} (\alpha)+\cos^{-1} (\alpha)=\pi/2 \] Where alpha is an angle:)

OpenStudy (maheshmeghwal9):

did u get that:)

OpenStudy (asnaseer):

but by using this substitution you are losing the restriction that:\[\cos^{-1}(x)=\sin^{-1}(x)\]

OpenStudy (maheshmeghwal9):

k! thanx I got it:)

OpenStudy (asnaseer):

so from your two solutions, you need to confirm which one satisfies the original problem

OpenStudy (asnaseer):

yw :)

OpenStudy (maheshmeghwal9):

:)

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