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Numerade Educator

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Problem 20 Easy Difficulty

Find the angle between the vectors. (First find an exact expression and then approximate to the nearest degree.)

$ a = 8i - j + 4k , b = 4j + 2k $

Answer

$84^{\circ}$

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Video Transcript

I'm going to find angle which will look after that is a equals to eight. I'm gonna stay plus four K. So equal to eight I minus of J. And plus a four K. Cap and be able to afford the place to go. So how we can find, we know that eight out B equals nothing but magnitude of in to be in the course of the triangle between them. Right? So obviously the product of these two is just the scalar. So we really want right into four. Right into over here I component and over here I component is zero and 18 to 0. So that would be zero and minus one and plus four to minus four plus four plus two plus eight. Equal to mine to the mentor of his route under 64 plus one plus 16. Okay. In the root under 16 plus four. In the course of tita right? We like mine four equals two. This will be 64 78 81 grouped under 81. The route under 20 I guess. Yeah. In the course of theater. So it will be caused to equals 2009. So I think it will be four upon 9 20. Right. So what will be the value of people? We need to just record that. So we need to how we can calculate that. We need for do you have to buy nine into road 20? So poor divided by 40.24 92 Where? So 40.2492 So poor divided by 40 point 2492 So this caused data that comes out to be nothing but 0.9938 So tita will because in first of 2.2993 Okay, So this will be the value of the court this time. Thanks