Inactive Tutor answered • 11/22/15
Tutor
New to Wyzant
sin(40) =opp/hyp
sin(40) =opp/80
(80)(sin(40)) =opp
opp =51.423
This is tricky because the triangle is upside down & the opposite side is actually the horizontal side AT THE TOP OF THE TRIANGLE. Remember that the hypotenuse never touches the 90deg right angle! That will help avoid using the hyp as adj.
The other less tricky way to solve this is to subtract 40 from 90 & solve the regular way using cos(50)=x/80. Draw it to see why.
Negative only makes sense if thinking of this in terms of quadrants.
Also, if your calculator is accidentally in radian mode you should get an answer of either 59.61 or 77.12 depending upon if you used sin(40) or cos(50) to solve.
Inactive Tutor
The answer seems right- I checked it two different ways. Since you know the answer, I'm assuming this is a previous test that has been graded already.. then again if your instructor graded it already he/ she should have caught that while grading. Be sure to follow the rules so you are not kicked off this site.. can someone give feedback?!
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11/22/15
Inactive Tutor
I also got the number 51.423, yet the vector is to the West and therefore in QII, so the number would be negative.
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11/22/15
Inactive Tutor
Agreed- I guess to keep this clear the problem should not mix quadrants and bearings but reflect an answer of 51.423 units west for the horizontal component.
Also, sorry for the harshness. You are probably using this correctly, its just I've seen some use WyzAnt Answers for online tests, etc.
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11/22/15
Tumaiesla G.
No worries. This was a take-home test for my math club, and the professor gave us permission to use the internet and any other resources. I aprecciate your help :)
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11/22/15
Hilton T.
tutor
Scott,
"Also, if your calculator is accidentally in radian mode you should get an answer of either 59.61 or 77.12 depending upon if you used sin(40) or cos(50) to solve."
sin(40) = cos(50)
You cannot have different answers if you use one or the other. I assume you meant "cos(40) or cos(50)".
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11/22/15
Hilton T.
tutor
None of the answer choices has the correct answer.
The horizontal component of the vector is given by
Ax = A cos θ where θ is measured counterclockwise from the x axis.
In this case, θ = 90 + 40 = 130 D, A = 80
Ax = 80 cos 130 D = -51.4 N
The horizontal component of the vector is given by
Ax = A cos θ where θ is measured counterclockwise from the x axis.
In this case, θ = 90 + 40 = 130 D, A = 80
Ax = 80 cos 130 D = -51.4 N
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11/22/15
Inactive Tutor
You are assuming that 50 radians plus 40 radians plus the right angle (π/2 radians) adds up to the inner triangle's angle sum π or is coterminal. 90 radians is not a right angle.
Plug sin(40rad) & cos(50rad) into your calculator.
That would work if it were 2π/9 instead of 40deg & 5π/18 instead of 50deg because they add up to π/2.
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11/22/15
Inactive Tutor
The bottom line is that several of us agree the answer is 51.4 in a westerly direction which is the same as -51.4 (negative is probably the answer the instructor is looking for judging by the list of possible answers).
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11/22/15
Tumaiesla G.
11/22/15