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britbrat4290

Solve the triangle. Round lengths to the nearest tenth and angle measures to the nearest degree. a = 7, b = 7, c = 5

  • 8 months ago
  • 8 months ago

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  1. britbrat4290
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    B. A = 69°, B = 69°, C = 42°??

    • 8 months ago
  2. mebs
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    sounds good.

    • 8 months ago
  3. britbrat4290
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    wrong

    • 8 months ago
  4. mebs
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    Try Using cosine law

    • 8 months ago
  5. mebs
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    \[7^{2} = 7^{2} + 5^{2} - 2(7)(5)cosA\]

    • 8 months ago
  6. britbrat4290
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    my answers need to be in degrees

    • 8 months ago
  7. mebs
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    you get \[cosA = \frac{ -25 }{ -70 }\] than do arc cosine. you get angle 69.07

    • 8 months ago
  8. britbrat4290
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    i need degrees for a b n c ??

    • 8 months ago
  9. mebs
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    you get angles 41.8 and 69.07. again

    • 8 months ago
  10. britbrat4290
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    A. A = 70°, B = 70°, C = 40° B. A = 69°, B = 69°, C = 42° C. A = 42°, B = 69°, C = 69° D. A = 69°, B = 42°, C = 69°

    • 8 months ago
  11. mebs
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    |dw:1375984676609:dw| ?

    • 8 months ago
  12. mebs
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    Try D.

    • 8 months ago
  13. mebs
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    have to go.

    • 8 months ago
  14. britbrat4290
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    thanks

    • 8 months ago
  15. britbrat4290
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    deff not 69 deg

    • 8 months ago
  16. genius12
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    Note that the triangle is isosceles:|dw:1375984026354:dw|

    • 8 months ago
  17. britbrat4290
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    ok ? still confused

    • 8 months ago
  18. genius12
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    Now use the cosine law:\[\bf a^2=b^2+c^2-2bc \cos(A) \implies 5^2=7^2+7^2-2(7)(7)\cos(A)\]Note that 'A' is the angle opposite side BC. Now re-arrange and solve for cos(A):\[\bf \implies \cos(A)=\frac{-73}{-98}=0.7445 \implies \cos^{-1}(0.7445)=A=41.884 \ degrees\]

    • 8 months ago
  19. genius12
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    Now because the triangle is isosceles, the remaining two angles B and C are equal so we can find each of them by subtracting A from 180 and dividing the result by 2:\[\bf \angle B=\angle C=\frac{ 180 -41.884}{ 2 }=69.058 degrees\]Rounding off our results to the nearest degree we get:\[\bf \angle A =42 \ degrees\]\[\bf \angle B=\angle C=69 \ degrees\] @britbrat4290

    • 8 months ago
  20. genius12
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    @britbrat4290 So your answer is correct =]

    • 8 months ago
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