Mathematics Times – July 2019

(I) 2 r MN  3 3 4 4 12^2 ^2    r 6

centre C of circle C 3 lies on

4

3

y x

Let

4

,

3

C h h 

 

12

3 3

2

OC MC OM    

2 16 2 3 5 3 9

9 3 5

h
 h  h     h

4 12

3 5

k h 

^

18 12

2 6

5 5

h k   

(II) Equation of line ZW
C C 1  2
^ 3 4 9x y 
Distance of ZW from (0, 0)

2 2

(^99)
3 4^5



Length of
2
2 3^2924
5 5
XY    
 
Distance of ZW from C
2 2
3 9 12
4 9
5 5 6
3 4^5

  


Length of
2
2
2
6 24 6
2 6
5 5
ZW  
^
length of
6
length of
ZW
XY

(III) Area of
1 1 72 6
2 2 5
MZN NM ZW   
 
Area of
1 1 24 6
( )
2 2 5
ZMW ZW OM OP    
9 288 6
3
5 25
 
  
 
Area of 5
Area of 4
MZN
ZMW



(IV) Slop of tangent to C 1 at
1 3
4 / 3 4
M

  
 Equation of tangent y mx 3 1m^2
3 9
3 1
4 16
y  x 
3 15 4
5
4 4 3
x y
y x

      ...(i)
tangent to x^2 4(2 ) y is
2
'
'
x m y
m

  ...(ii)
Compare (i) and (ii)
4
'
3
m  and
2 10
5
m' 3

   