InterviewSolution
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InterviewSolution
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The product of y the perpendiculars from the two points `(pm 4, 0)` to the line `3x cos phi +5y sin phi =15` isA. 25B. 16C. 9D. 8 |
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Answer» Correct Answer - C If the length of perpendicular be `p_(1)` from the point (4, 0) `p_(1)=|(12 cos phi -15)/sqrt((3 cos phi)^(2)+(5 cos phi)^(2))|` `=(15-12 cos phi)/sqrt((3 cos phi)^(2)+(5 cos phi)^(2))` If length of perpendicular be `p_(2)` from the point (-4, 0) `P_(2)=|(-12 cos phi -15)/sqrt((3 cos phi)^(2)+(5 cos phi)^(2))|` `=((12 cos phi +15))/sqrt((3 cos phi)^(2)+(5 sin phi)^(2))` `p_(1).p_(2)=((15-12 cos phi)(12 cos phi +15))/((3 cos phi)^(2)+(5 sin phi)^(2))` `=((225-144 cos^(2) phi))/(9 cos^(2) phi + 25 sin^(2) phi)=(9(25-16 cos^(2) phi))/(25-16 cos^(2) phi)` `=9` |
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