If m = (cos θ – sin θ) and n = (cos θ + sin θ) then show that 
Given: m = (cos θ – sin θ)
n = (cos θ + sin θ)
Now,
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Multiply numerator and denominator by cos θ – sin θ :
Therefore,
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Now,
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Multiply numerator and denominator by cos θ + sin θ :
Therefore,
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= ![]()
Now, consider
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Divide numerator and denominator by cos θ:
= 
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Therefore,
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Hence, proved.