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Math Help - No trigonometry use? triangle in a square.

  1. #1
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    No trigonometry use? triangle in a square.

    ABCD is a square and ECD an isosceles triangle
    with base angles 15 degrees, as shown in the figure. Prove that Angle AEB = 60 degrees (and therefore triangle AEB is equilateral), without using trigonometry.
    Is this impossible? thanks for your help.
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  2. #2
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    Quote Originally Posted by Intsecxtanx View Post
    ABCD is a square and ECD an isosceles triangle
    with base angles 15 degrees, as shown in the figure. Prove that Angle AEB = 60 degrees (and therefore triangle AEB is equilateral), without using trigonometry.
    Is this impossible? thanks for your help.
    I just did it. I got that AEB is equilateral.
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  3. #3
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    Its easy to demonstrate that AEB can equilateral... but I have no idea how to prove this is the only available option.
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  4. #4
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    Quote Originally Posted by Intsecxtanx View Post
    ABCD is a square and ECD an isosceles triangle
    with base angles 15 degrees, as shown in the figure. Prove that Angle AEB = 60 degrees (and therefore triangle AEB is equilateral), without using trigonometry.
    Is this impossible? thanks for your help.
    Angle AED = BEC. Angle DEC = 150. AED + BEC + DEC + AEB = 360.

    Angle ADE = 75. Angle DAE = 90 - EAB. ADE + DAE + AED = 180.

    I believe solving this system gives that the angles of the triangle are 60.
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