vmathhelp 2 years ago Can someone help me with Geo Problem! Diagonal AC divides a trapezoid ABCD two similar triangles ABC and ACD. Find AC if BC=4cm and AD=9cm

1. vmathhelp

@ganeshie8 I need help

2. vmathhelp

@ghazi @lalaly @AccessDenied

3. kajolc.2496

Are these triangles similar by area?

4. kajolc.2496

Is not there any fig. for this?

5. campbell_st

I think it looks like this|dw:1356206771435:dw| the angles marked x are equal by alternate angles in parallel lines

6. ghazi

|dw:1356207039082:dw|

7. vmathhelp

Now what do i do?

8. ghazi

have you provided whole information?

9. vmathhelp

yes

10. kajolc.2496

I think there is something we r missing..

11. campbell_st

well the corresponding sides in the triangles are triangle ABC and triangle ACD are AB AC AB DC BC AD now you need to use the ratio's of corresponding sides in similar triangles

12. kajolc.2496

but ques. does'nt say that it divides the triangles in equal areas!

13. kajolc.2496

that's wat i was confirming earlier

14. vmathhelp

15. kajolc.2496

SIMILARITY CAN ONLY BE USED WHEN AREAS ARE EQUAL

16. campbell_st

oops corresponding side should be AC and DC so using the ratio of corresponding sides $\frac{4}{9} = \frac{AB}{AC}= \frac{AC}{ DC}$

17. vmathhelp

what happens next?

18. vmathhelp

@campbell_st

19. campbell_st

who knows.... it doesn't make sense to me... there seems to be something missing from the question.

20. campbell_st

Oh, and triangles can be similar and have different areas the ratio will be the linear ratio squared. so the ratio of areas in the triangles is ABC:ACD = (4/9)^2

21. vmathhelp

@ghazi is there missing info?

22. ghazi

i am confused

23. vmathhelp

wat r u confused about?

24. ghazi

there is something missing in it