## anonymous one year ago 5. Triangle ABC has an angle of 90 degrees at B. Point A is on the y axis, AB is part of the line x-2y+8=0 and C is the point (6,2) (iii) Answer = AB equals the square root of 20 BC equals the square root of 20 Area of triangle equals 10 (iv) Using your answer to (iii), find the length of the perpendicular from B to AC. I don't even know where to start here, what is the method for figuring this out? And do they mean a line perpendicular to AC meeting B?

1. anonymous

ok just making sure, the stuff you have for (iii) are distances you've already solved for?

2. anonymous

Yes, and I checked the answers at the back of my book already so they are definitely correct.

3. anonymous

Would it help to upload a picture of the triangle?

4. anonymous

yes definitely

5. anonymous

Ok give me a second....

6. anonymous

7. anonymous

That is the triangle they have on the answers side of the book (the very first question was to draw it which i did successfully)

8. anonymous

awesome :) ok. so it's saying the line from AC is $$x+3y-12=0$$ so we need the line perpendicular AC that passes through B.

9. anonymous

Did you solve for a point for B?

10. anonymous

The point B is at (4,6) is that what you mean?

11. anonymous

yes. there's a formula for this, the distance between a point and a line http://www.intmath.com/plane-analytic-geometry/perpendicular-distance-point-line.php But if you don't want to use that, we have to find the equation for the perpendicular line, then find the intersection point, then find the length of the segment

12. anonymous

Ok, thats great and I could use that but would that be using the answers i got in the last question?

13. anonymous

ok. I got you. Use the Pythagorean theorem to find the base of the triangle $\sqrt{20}^2+\sqrt{20}^2=b^2$ Then use the formula for area of a triangle $10=bh$ |dw:1441203786360:dw|

14. anonymous

wow I'm a dummy. Area of a triangle is ½bh not just bh

15. anonymous

you follow?

16. anonymous

oh good I thought I was doing something wrong, yes let me just try it quickly to make sure I understand...

17. anonymous

hmmmm I am getting square root of ten not just ten. My working out is: square root of 40 = b 10=1/2 x square root of 40 x h 10= square root of 10 x h square root of 10 = h

18. anonymous

yes, √10 is correct

19. anonymous

Oh sorry, have been making silly mistake with the maths all day, thank you so very much! You have helped me a lot!

20. anonymous

you're welcome.