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MakcuM [25]
3 years ago
10

If vector u has its initial point at (-7, 3) and its terminal point at (5, -6), u =

Mathematics
1 answer:
attashe74 [19]3 years ago
6 0

First of all, let <span>θθ</span> be some angle in <span><span>(0,π)</span><span>(0,π)</span></span>. Then

<span><span><span>θθ</span> is acute <span>⟺⟺</span> <span><span>θ<<span>π2</span></span><span>θ<<span>π2</span></span></span> <span>⟺⟺</span> <span><span>cosθ>0</span><span>cos⁡θ>0</span></span>.</span><span><span>θθ</span> is right <span>⟺⟺</span> <span><span>θ=<span>π2</span></span><span>θ=<span>π2</span></span></span> <span>⟺⟺</span> <span><span>cosθ=0</span><span>cos⁡θ=0</span></span>.</span><span><span>θθ</span> is obtuse <span>⟺⟺</span> <span><span>θ><span>π2</span></span><span>θ><span>π2</span></span></span> <span>⟺⟺</span> <span><span>cosθ<0</span><span>cos⁡θ<0</span></span>.</span></span>

Now, to see if (say) angle <span>AA</span> of the triangle <span><span>ABC</span><span>ABC</span></span> is acute/right/obtuse, we need to check whether <span><span>cos∠BAC</span><span>cos⁡∠BAC</span></span> is positive/zero/negative. But what is <span><span>cos∠BAC</span><span>cos⁡∠BAC</span></span>? It is the angle made by the vectors <span><span><span>AB</span><span>−→−</span></span><span><span>AB</span>→</span></span> and <span><span><span>AC</span><span>−→−</span></span><span><span>AC</span>→</span></span>. (When you are computing the angle at a particular vertex <span>vv</span>, you should make sure that both the vectors corresponding to the two adjacent sides have that vertex <span>vv</span> as the initial point.) We will first compute these two vectors:

<span><span><span><span>AB</span><span>−→−</span></span>=(0,0,0)−(1,2,0)=(−1,−2,0)</span><span><span><span>AB</span>→</span>=(0,0,0)−(1,2,0)=(−1,−2,0)</span></span><span><span><span><span>AC</span><span>−→−</span></span>=(−2,1,0)−(1,2,0)=(−3,−1,0)</span><span><span><span>AC</span>→</span>=(−2,1,0)−(1,2,0)=(−3,−1,0)</span></span>Therefore, the angle between these vectors is given by:<span><span><span>cos∠BAC=<span><span><span><span>AB</span><span>−→−</span></span>⋅<span><span>AC</span><span>−→−</span></span></span><span>|<span><span>AB</span><span>−→−</span></span>||<span><span>AC</span><span>−→−</span></span>|</span></span>=…</span>(1)</span><span>(1)<span>cos⁡∠BAC=<span><span><span><span>AB</span>→</span>⋅<span><span>AC</span>→</span></span><span>|<span><span>AB</span>→</span>||<span><span>AC</span>→</span>|</span></span>=…</span></span></span>Can you take it from here? From the sign of this value, you should be able to decide if angle <span>AA</span> is acute/right/obtuse.

Now, do the same procedure for the remaining two angles <span>BB</span> and <span>CC</span> as well. That should help you solve the problem.

A shortcut. Since you are not interested in the actual values of the angles, but you need only whether they are acute, obtuse or right, it is enough to compute only the sign of the numerator (the dot product between the vectors) in formula (1). The denominator is always positive.

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They can only sit one way because they are still in a row
Or did you mean like how many different ways can they sit?
8 0
2 years ago
Please help me asap<br> math
Stella [2.4K]

Answer:

I think 478.4   ._.

Step-by-step explanation:

First, find out how many gallons of gasoline she can buy with $18.50 by dividing 18.50 by 1.25 to get 14.8 gallons. Then, since he already has 6 gallons in his tank, add 6 to 14.8 = 20.8. Finally multiply this by the ratio of gallons to miles (23) to get 478.4

3 0
3 years ago
According to his car odometer,Alfonso drove a total of 10 kilometers from his house to the movie theater and back again approxim
Brums [2.3K]

Answer:

It is approximately 3.10 miles from Alfonso's house to the movie theater

Step-by-step explanation:

First, identify what you know:

1) Alfonso drove from his house TO the movie theater, and then BACK to his house.

2) Alfonso's odometer shows him that the ENTIRE trip was 10 miles.

If the entire trip was 10 miles, and he only went to the move theater, AND took the same route back, then we simply divide 10 in half! This will give us the distance from his house the the movie theater, or rather, half of the trip, in kilometers.

10/2 = 5 kilometers.

Now, what is 5 kilometers in miles? Well, one mile is equal to 1.60934 kilometers, and one kilometer is equal to 0.621371 miles. So, simply multiply!

5 km  x 0.621371 miles = 3.106855

The approximate distance from his house to the theater is 3.10 miles!

Hope this helps! :)

3 0
3 years ago
What number gives a result of −5 when 9 is subtracted from the quotient of the number and 6?
My name is Ann [436]

Answer:

25

Step-by-step explanation:

If it gives a result of -4 then our equation will have .... = -4

 

If we subtract 9 from the quotient of a number and 5 we have  x/5 - 9

 

Our equation is:

 

x/5 - 9 = -4     add 9 to both sides

x/5 = -4 + 9

x/5 = 5           multiply both sides by 5

x = 5(5)

x = 25

Check:  25/5 - 9 = 5-9 = -4

           Answer checks as correct from information given

 

8 0
3 years ago
Given that f(x) = 5x^2-3x+7 and f(g(x))=(5x^4)/9 + (17x^2)/3 + 21. Find all possible values for the sum of the coefficients in t
shtirl [24]

steps

(x) = 5x^2-3x+7

refine

x=5x^2-3x+7

Switch sides

5x^2-3x+7-x=x-x

Subtract x from both sides

5x^2-4x+7=0

Solve with the quadratic formula

8 0
3 years ago
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