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If the line ` y cos alpha = x sin alpha +a cos alpha ` be a tangent to the circle `x^(2)+y^(2)=a^(2)`, thenA. `sin^2alpha=1`B. `cos^2alpha=1`C. `sin^2alpha=a^2`D. `cos^2alpha=a^2` |
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Answer» Correct Answer - D Given , `y=xtan alpha+a` Condition for tangency is `a^2=a^2(1+tan^2alpha)[because c^2=a^2(1+m^2)]` `rArr sec^2alpha=1rArr cos^2=1` |
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