JEE MainMathematicsComplex NumbersMCQ+4 / −1
If and is real, then the point represented by the complex number z lies :
- Aeither on the real axis or a circle passing through the origin.
- Bon a circle with centre at the origin
- Ceither on real axis or on a circle not passing through the origin.
- Don the imaginary axis.
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Correct answer: A
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Let where and .
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Given that is real. A complex number is real iff its imaginary part is zero.
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Compute: and
So,
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Rationalize the denominator:
We only need the imaginary part of the numerator.
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Let Then numerator is
Its imaginary part is
Therefore,
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Simplify:
Hence either or
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Interpret geometrically:
- represents the real axis.
- which is a circle with centre and radius .
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Check whether this circle passes through the origin: At , so the origin lies on the circle.
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Therefore, the point represented by lies either on the real axis or on a circle passing through the origin.
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Hence the correct option is:
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