## GoldRush18 Group Title The circle C has equation (x-3)^2+(y-4)^2=25. i. State the radius and the coordinates of the centre of C. ii. Find the equation of the tangent at the point (6,8) on C. iii. Calculate the coordinates of the points of intersection of C with the straight line y=2x+3. 2 years ago 2 years ago

1. GoldRush18 Group Title

@experimentX

2. experimentX Group Title

where do you have problem??

3. GoldRush18 Group Title

part 2

4. experimentX Group Title

let y=mx+c be equation of your tangent |dw:1336583832242:dw|

5. experimentX Group Title

find the value of m2 put the all the values m2, (6,8) in y = mx + c ... and find the value of c. then you have tangent!!

6. GoldRush18 Group Title

7. experimentX Group Title

$(x - 3)^2 + ((2x+3) - 4)^2 = 25$ Find the value of x, and put the value of x in equation of circle ... and find corresponding y

8. GoldRush18 Group Title

ok im still on part 2 when it comes to graph and stuff i just cant get it thanks though

9. experimentX Group Title

you know how to find slope ... ?? from two points??

10. GoldRush18 Group Title

nope

11. GoldRush18 Group Title

is that the same thing as the gradient

12. experimentX Group Title

yes ... $m = \frac{y_2 - y_1}{x_2 - x_1}$

13. GoldRush18 Group Title

and i got 4/3

14. experimentX Group Title

allright you know when two lines are perpendicular, if m1 and m2 be their gradient or slope then $$m_1 * m_2 = -1$$ ??

15. GoldRush18 Group Title

no i didnt know that so what are the values i should include for this part

16. experimentX Group Title

m1 is just you calculated ... slope(gradient) of that radius!! m2 .. you have to calculate!! using the relation above.

17. GoldRush18 Group Title

i got 0

18. experimentX Group Title
19. experimentX Group Title

No .. you should get m1*m2 = -1 (m1 = 4/3) m2 = -3/4

20. GoldRush18 Group Title

ok i got it now

21. GoldRush18 Group Title

how do i get C which is the y intercept?

22. experimentX Group Title

you know one point ... so it satisfies that equation m = -3/4 (x,y) = (6,8) y = mx+c, c=??

23. GoldRush18 Group Title

i got y=-3/4x+25/2

24. experimentX Group Title

Oo .. put the values of x=6 and y=8 since (x,y) is solution and we already know this!!

25. GoldRush18 Group Title

ok i understand now

26. GoldRush18 Group Title

im gonna try part c

27. GoldRush18 Group Title

and im stuck once more

28. experimentX Group Title

put y = 2x+3 on (x-3)^2+(y-4)^2=25 and find the value of x