Solving Oblique Triangle

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This video gives one example of finding all the sides and angles of an oblique triangle when you are given the lengths of two sides and the measure of the angle between those two sides. See below for some clarification of the common questions.

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Finding b...

2*9*10 = 180

81 + 100 = 181

cos(109°) ≈ -0.3256 use a calculator for this. If you get -0.5770, then your calculator is set to radians instead of degrees

181 - 180*(-0.3256) ≈ 181 - (-58.6023) = 181 + 58.6023 ≈ 239.60

sqrt(239.60) ≈ 15.48

Finding A...

Use b = 15.48 and use Law of Sines...

109 is the given measure of angle B

sin A = (9 * sin(109°)) / 15.48 ≈ (9 * 0.9455) / 15.48 NOTE: sin(109°) ≈ 0.9455 If you get 0.8167, then your calculator is set to radians instead of degrees

sin A ≈ 0.5497

After this, you need to use the inverse sine function on your calculator (and make sure your calculator is STILL set for degrees and not radians)...

A = sin-1(0.5497)

A ≈ 33.3478 °
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Finding b...

2*9*10 = 180

81 + 100 = 181

cos(109°) ≈ -0.3256 use a calculator for this. If you get -0.5770, then your calculator is set to radians instead of degrees

181 - 180*(-0.3256) ≈ 181 - (-58.6023) = 181 + 58.6023 ≈ 239.60

sqrt(239.60) ≈ 15.48

Finding A...

Use b = 15.48 and use Law of Sines...

109 is the given measure of angle B

sin A = (9 * sin(109°)) / 15.48 ≈ (9 * 0.9455) / 15.48 NOTE: sin(109°) ≈ 0.9455 If you get 0.8167, then your calculator is set to radians instead of degrees

sin A ≈ 0.5497

After this, you need to use the inverse sine function on your calculator (and make sure your calculator is STILL set for degrees and not radians)...

A = sin-1(0.5497)

A ≈ 33.3478 °

MathWithMisterA
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OH!!! THANK YOU SO MUCH!! <3 YOU HELPED ME WITH MY I.W. TOMMOROW!!

furruppe
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In 2:48, I think that's 239.61, because you round it to nearest hundreds. Please correct me if I'm wrong

AceuPH
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At the 2:30 i have entered that into my calculator in every way i can. Exactly as you say. In both radian and degree. And not once did i ever get 239.60. Please explain. This doesn't make any sense to me.

caseys
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btw thanks it helps me a lot even i cant figure out how you get the A

FryzzlethePork
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YOO I DIDNT UNDERSTAND THIS BUT NOW I DO!!! THAT YOU SO MUCH!!!!

prodrifter
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It's really good, just take it a bit slower.

TonyPunisher
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May I ask how you got the 239.60 what did you solve to get that number? And the b= 15.48 (Please Reply ASAP our exam is tommorow)

rakashindcserver
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How did you get the answr for b=15.48?

Colateugar
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2:50
His answer should be Negative 15.48. Number dont just magically go positive.

BlackWolf-krwo
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Its possible you solve 3 sides with given 3 angles?

juliuscaezarroldan
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How did you get b=15.48
...reply asap please..my last submission is tomorrow

kyorye