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If `(|a+b|)/(|a-b|)=1`, then the angle between `a` and `b` isA. `0^(@)`B. `45^(@)`C. `90^(@)`D. `60^(@)` |
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Answer» (c) `(|a+b|)/(|a-b|)=1` or `|a+|=|a-b|` or `sqrt(a^(2)+b^(2)+2ab cos alpha)=sqrt(a^(2)+b^(2)-2ab cos alpha)` or `a^(2)+b^(2)+2ab cos alpha=a^(2)+b^(2)-2ab cos alpha` or` 4ab cos alpha=0` or `cos alpha=0` or `alpha=90^(@)` |
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