ICSE Class 10 Answered
A hemisphere and a cone have equal bases.If their heights are also equal,then what is the ratio of their curved surfaces.
2.find the image of the point (-3,1) in the line 2x-3y=4.
Asked by Farheen1447 | 07 Mar, 2019, 06:10: PM
Expert Answer
curved surface of hemisphere = 2πr2 sq.units
curved surface of cone = sq.units
[ radius of base of hemisphere and base of cone are same. Height of the hemisphere is same as radius.
Height of cone is same as height of hemisphere ]
ratio of curved surface area of hemisphere to that of cone = √2
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point P(-3, 1) is on the line which is perpendicular to the line 2x-3y = 4.
Hence point P(-3, 1) is on the line 3x+2y = k , where k is to be determined .
3(-3) + 2(1) = - 7 Hence the perpendicular line is 3x+2y = -7
Coordinates of point of intersection Q is obtained by solving the equations of the two lines
2x -3y = 4 ........................(1)
3x +2y = -7 ......................(2)
eqn.(1)×3 is : 6x -9y = 12 ................(3)
eqn.(2)×2 is : 6x +4y = -14 ...............(4)
eqn.(3) - eqn.(4) gives, -13y = 26 or y = -2
substituting y = -2 in eqn.(1), we get x = -1
hence point of intersection is Q (-1, -2)
Q is the middle point of P and image of P i.e., P'(x,y)
hence (x-3)/2 = -1 or x = 1 ; similarly (y+1)/2 = -2 or y = -5
hence image point is ( 1, -5)
Answered by Thiyagarajan K | 07 Mar, 2019, 08:34: PM
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