<p>Someone needs to start a list</p>
<p>For the vector one i used cos50 :/. why do you have to use 130?</p>
<p>the vector one i guessed 
cause 4 and 8 form a triangle so 12 can’t work
5.something can’t work either, since the mystery side is the longest
so it was either 8.6 or 11? i put 11</p>
<p>130 degrees because we use Triangle Law Of Vector Addition.</p>
<p>nwgolfer321 you have to connect the vectors from end to tip or look at it as a parallelogram, the angle in between the two is 130… i dont know if that makes sense haha i got that one wrong but thats what you’re supposed to do and then you end up with 11</p>
<p>Michael, I just calculated the vector one. The correct answer’s 11. You got lucky!</p>
<p>^Oh and yeah, you could use Pianoman’s method too. That’s the paralellogram law of vector addition. Google 'em up.</p>
<p>it makes sense. i havent done that crap in 2 years lol. dang it. i can’t believe i spaced on that. i just solved for the third side in the triangle. 2 wrong…<em>sigh</em></p>
<p>it’s okay! you can miss up to 5 :P</p>
<p>You do not have to do it that way.
If any of you took physics, you can just use vector addition.
Do cos(50) * 4. You find the x component of that vector.
Then at it to 8 because that is the x component of the second vector.
Then you do sin(50)<em>4 to find the y component. Since the vector (8) does not have a y component, just assume that sin(50)</em>4 is the only y component.
Then use the sum of the x and y components and put them into Pythagorean theorem.
You get 11.005</p>
<p>for the vector one–shouldn’t it be about a little less than 10 cause 130 is about in the middle of 90 and 180 (and thus almost a 45degree diagonal). Therefore, it would make sense for the addition of the 4 unit vector to add about 2 units to the magnitude. (8 + 2 = 10). </p>
<p>I kmow I didn’t actually calculate it, but I would think 11 would mean that the angle is almost a straight line.</p>
<p>^ wow i’m in ap phys. b and i forgot about that
very cool</p>
<p>lawdertrain, you have to consider the y component of the 4 unit vector!
It still affects the magnitude of the vector as a whole!</p>
<p>And I think I got the one wrong where it was like sin(x)=n (it gave you n, i just forget it), then said cos(x/2)=? I forgot the formula so I just found x, divided it by 2 and found the cos :(</p>
<p>lawder it’s a bit over 45 degrees, so you’ have to add a bit more than 2 to the magnitude</p>
<p>oh yea wow i forgot about the y component</p>
<p>Oh, no. I just checked the formula book. 11 cant be the answer.
Using Triangle Law of Vector Addition,
We use the formula-</p>
<p>Resultant= [a^2 + b^2 + 2ab cos theta]^1/2</p>
<p>So according to that, a= 4 , b=8 , theta= 130</p>
<p>We get Resultant= 6.23. Was this even a choice? I don’t remember, but this is the correct methodology.</p>
<p>nwgolfer- haha i think that’s what you’re supposed to do. at least that’s what i did… nothing wrong with it right?</p>
<p>The answer is not 6.23. It’s wrong.</p>
<p>perfect that makes no sense though… 
the top angle was 130, so that means the side opposite would be the longest of the three sides</p>
<p>its -2ab, not plus</p>