tutorinseoul Posted March 20, 2017 Report Share Posted March 20, 2017 Hi everyone, hope you will enjoy this question! 2 Reply Link to post Share on other sites More sharing options...
IB`NOT`ez Posted March 22, 2017 Report Share Posted March 22, 2017 (edited) I really like this question, but my god it's the hardest Vectors question I've ever attempted doing since I mostly stick to Section A Maths HL questions only when practicing HL. Also, would it be possible for you to PM me the answers? Also wondering if all the questions you've posted so far are all Paper 1 questions, or if they require calculator, you'll point it out. Thanks and keep up with the questions! Doing my best to do them all! Edited March 22, 2017 by IB`ez Reply Link to post Share on other sites More sharing options...
tutorinseoul Posted March 22, 2017 Author Report Share Posted March 22, 2017 Heya, this is SL and paper 2 :)! share your answer and i will check them! Reply Link to post Share on other sites More sharing options...
7sstu Posted March 27, 2017 Report Share Posted March 27, 2017 Do you have answers please? Reply Link to post Share on other sites More sharing options...
IBstudent21 Posted March 27, 2017 Report Share Posted March 27, 2017 (edited) 8. a) i. AB = AO + OB = (3, 1, 7) ii. |AB|= (9+1+49)^0.5= (59)^0.5 b) OC - OA= AC (x+1)= -1 Cx=-2 (y-0)= 1 Cy=1 (z-4)= -1 Cz=3 c) i. angle ADB= 180-theta ii. Area of triangle ABD= 1/2 (BD) (AD) (sin180-theta) d) ( (1/2) (BD) (AD) (sin180-theta) ) / (1/2) (AD) (DC) (sintheta) =3 (BD) (sin180-theta) / (DC) (sintheta) =3 BD/DC=3 BD=3DC DC=BD/3 Since BC= BD + DC BC= BD + (1/3) BD = (4/3) BD Therefore, BD/BC=3/4 e) 4BD=3BC 4x-16=3(6) 4x=24 Dx=10 4y-4=3(0) Dy=1 4z-12=3(0) Dz=3 * I'm not sure whether these are correct * Edited March 27, 2017 by IBstudent21 Reply Link to post Share on other sites More sharing options...
kw0573 Posted March 30, 2017 Report Share Posted March 30, 2017 On 3/27/2017 at 2:01 PM, IBstudent21 said: 8. a) i. AB = AO + OB = (3, 1, 7) If AB = AO + OB, what is AO and how do you add that to OB? Reply Link to post Share on other sites More sharing options...
IBstudent21 Posted March 31, 2017 Report Share Posted March 31, 2017 13 hours ago, kw0573 said: If AB = AO + OB, what is AO and how do you add that to OB? I just saw the mistake I made!! I saw it as OA, and therefore added the vector OA to OB. AO is still easy to find though, so you just flip the signs, since OA= -AO. Therefore, AO becomes (1,0,-4) So, AB= (5,1,-1) |AB| changes as well, I'll fix both in my other post later. Thanks for checking it for me! I hope something like that doesn't happen in either of my papers. I keep making these stupid mistakes everywhere. Reply Link to post Share on other sites More sharing options...
kw0573 Posted March 31, 2017 Report Share Posted March 31, 2017 On 3/27/2017 at 2:01 PM, IBstudent21 said: e) 4BD=3BC 4x-16=3(6) 4x=24 Dx=10 Similarly, you if you write OB = (4, 1, 3) beside OC = (-2, 1, 3). It should be clear that D, on line segment BC, has a x coordinate between -2 and 4. Reply Link to post Share on other sites More sharing options...
IBstudent21 Posted March 31, 2017 Report Share Posted March 31, 2017 49 minutes ago, kw0573 said: Similarly, you if you write OB = (4, 1, 3) beside OC = (-2, 1, 3). It should be clear that D, on line segment BC, has a x coordinate between -2 and 4. Oh yeah, you're right. How do I find it though, if it isn't the midpoint? Is the method I used wrong? Reply Link to post Share on other sites More sharing options...
kw0573 Posted March 31, 2017 Report Share Posted March 31, 2017 (edited) 7 minutes ago, IBstudent21 said: Oh yeah, you're right. How do I find it though, if it isn't the midpoint? Is the method I used wrong? 3BCx is not 18. Edited March 31, 2017 by kw0573 Reply Link to post Share on other sites More sharing options...
IBstudent21 Posted March 31, 2017 Report Share Posted March 31, 2017 16 minutes ago, kw0573 said: 3BCx is not 18. Is it -18? Reply Link to post Share on other sites More sharing options...
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