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Copythat

  • 3 years ago

In the figure at right, it is given than BDC is straight, BD = DA, and AB = AC = DC. Find the size of angle C

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  1. Copythat
    • 3 years ago
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    |dw:1351641146982:dw|

  2. asnaseer
    • 3 years ago
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    do you know what an isosceles triangle is and what its properties are?

  3. Copythat
    • 3 years ago
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    Yeah. I figured angles B and DAB must be equal, angles CDA and CAD must be equal, and angles B and C must be equal

  4. asnaseer
    • 3 years ago
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    you are almost there - now assign a symbol to angle ABD - lets call it x, and fill-in all the other angles you know using this symbol, e.g. from what you have already said we get: |dw:1351641960334:dw| now find y in terms of x and then use the property of the sum of the angles in a triangle to solve for x.

  5. asnaseer
    • 3 years ago
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    have you understood how to proceed?

  6. asnaseer
    • 3 years ago
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    HINT: Use the angle sum of a triangle in triangle CAD to express y in terms of x.

  7. Copythat
    • 3 years ago
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    Using triangle CAD, y = (180-x)/2?

  8. Copythat
    • 3 years ago
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    I plugged that in for y: 180=3x+[(180-x)/2] And found x=36

  9. Copythat
    • 3 years ago
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    Thanks for your help

  10. asnaseer
    • 3 years ago
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    yw :)

  11. asnaseer
    • 3 years ago
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    And your answer agrees with the one I got as well :)

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