## ranxu6j3 2 years ago Excuse me, please 3 vectors (they are not 0), |a|=5 |b|=3 the angle between a and b is 60 to balance , |c|=?

1. ranxu6j3

|dw:1361102188359:dw|

2. ranxu6j3

@ParthKohli can you help?

3. ParthKohli

No, I am not well-versed in vectors :-(

4. ZeHanz

Try putting a coordinate system on it, with a or b as one of the axes. Let's say b is the negative x-axis. Then you can write a as the sum of its x- and y-components. I will make a drawing to explain...

5. ranxu6j3

thanks @ParthKohli , cuz there was nobody viewing, and I'm your fan, so I tried to ask you. that's alright, thanks for replying

6. ranxu6j3

thanks , @ZeHanz , I'll wait for your illustration.

7. ZeHanz

Here it is: (try to get the lengths of a_x and a_y, the x and y components of a.

8. ZeHanz

Once you have these values, you can add up all the x-components (there are 2). There is also only one y-component (that of a). To get c, you'll have to compensate in the opposite direction, so take the opposite values of the x- and y-components. Hope this is clear enough ;)

9. ranxu6j3

cool how did you draw that? tks a lot, in your way that I'll get c=5.5, is it? but the answer is 7, am I misunderstanding or? sorry for being confused ,still your pic is very clear

10. ranxu6j3

oh sorry, wrong considering , give me a moment

11. ZeHanz

I used Geogebra. Look it up at geogebra.org (it's free).

12. ranxu6j3

ok , my bad ,i got 7

13. ranxu6j3

thank you very much, i was stupidly stuck, and thanks for telling me the app, i think it will be useful

14. ZeHanz

Here's another drawing. The sum of the x-components is -5 + -2.5 = -7.5. The only y-component is 2.5√3. (there is a 30-60-90-triangle involved). So to compensate, c should go 5.5 to the right and 2.5√3 down: (lenght is indeed 7!)

15. ranxu6j3

yeah i got 7 when i told you i got it, thank you very much sorry for having a wrong considering at first, i can't thank you enough for your patience and enthusiasm of answering me. i can imagine what's going on when you gave me first picture. thaks again

16. ZeHanz

You're welcome!