Trigonometry problem gives a wrong answer












1












$begingroup$


img



A. Find the BC.



Information: <) BAC = 65 (the base), AD = 10



I could not get it to work.



What I did is, I took ADB and then I divided 65 by 2 so BAD = 32.5.



Now I need to find BD so I did



tan (32.5) * 10 = 6.37 * 2 = 12.74


so BC = 12.74, but in the book the answer is 8.12, what did I do wrong?










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$endgroup$












  • $begingroup$
    because you are assuming that AD is bisector, which is not given moreover AD is not perpendicular to BC, at least it is not given
    $endgroup$
    – newzad
    Nov 6 '13 at 17:18












  • $begingroup$
    I think you need another piece of information. So far you only have an angle and a side. Are $AE$ and $CE$ altitudes?
    $endgroup$
    – Rocket Man
    Nov 6 '13 at 17:25










  • $begingroup$
    What is $E$? Is the triangle isosceles? How is $D$ defined?
    $endgroup$
    – pi37
    Nov 6 '13 at 17:36










  • $begingroup$
    The length of AD to the base BC is 10 cm
    $endgroup$
    – Roy
    Nov 6 '13 at 17:40
















1












$begingroup$


img



A. Find the BC.



Information: <) BAC = 65 (the base), AD = 10



I could not get it to work.



What I did is, I took ADB and then I divided 65 by 2 so BAD = 32.5.



Now I need to find BD so I did



tan (32.5) * 10 = 6.37 * 2 = 12.74


so BC = 12.74, but in the book the answer is 8.12, what did I do wrong?










share|cite|improve this question











$endgroup$












  • $begingroup$
    because you are assuming that AD is bisector, which is not given moreover AD is not perpendicular to BC, at least it is not given
    $endgroup$
    – newzad
    Nov 6 '13 at 17:18












  • $begingroup$
    I think you need another piece of information. So far you only have an angle and a side. Are $AE$ and $CE$ altitudes?
    $endgroup$
    – Rocket Man
    Nov 6 '13 at 17:25










  • $begingroup$
    What is $E$? Is the triangle isosceles? How is $D$ defined?
    $endgroup$
    – pi37
    Nov 6 '13 at 17:36










  • $begingroup$
    The length of AD to the base BC is 10 cm
    $endgroup$
    – Roy
    Nov 6 '13 at 17:40














1












1








1





$begingroup$


img



A. Find the BC.



Information: <) BAC = 65 (the base), AD = 10



I could not get it to work.



What I did is, I took ADB and then I divided 65 by 2 so BAD = 32.5.



Now I need to find BD so I did



tan (32.5) * 10 = 6.37 * 2 = 12.74


so BC = 12.74, but in the book the answer is 8.12, what did I do wrong?










share|cite|improve this question











$endgroup$




img



A. Find the BC.



Information: <) BAC = 65 (the base), AD = 10



I could not get it to work.



What I did is, I took ADB and then I divided 65 by 2 so BAD = 32.5.



Now I need to find BD so I did



tan (32.5) * 10 = 6.37 * 2 = 12.74


so BC = 12.74, but in the book the answer is 8.12, what did I do wrong?







trigonometry






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 24 '18 at 7:20









Glorfindel

3,42981830




3,42981830










asked Nov 6 '13 at 17:15









RoyRoy

414




414












  • $begingroup$
    because you are assuming that AD is bisector, which is not given moreover AD is not perpendicular to BC, at least it is not given
    $endgroup$
    – newzad
    Nov 6 '13 at 17:18












  • $begingroup$
    I think you need another piece of information. So far you only have an angle and a side. Are $AE$ and $CE$ altitudes?
    $endgroup$
    – Rocket Man
    Nov 6 '13 at 17:25










  • $begingroup$
    What is $E$? Is the triangle isosceles? How is $D$ defined?
    $endgroup$
    – pi37
    Nov 6 '13 at 17:36










  • $begingroup$
    The length of AD to the base BC is 10 cm
    $endgroup$
    – Roy
    Nov 6 '13 at 17:40


















  • $begingroup$
    because you are assuming that AD is bisector, which is not given moreover AD is not perpendicular to BC, at least it is not given
    $endgroup$
    – newzad
    Nov 6 '13 at 17:18












  • $begingroup$
    I think you need another piece of information. So far you only have an angle and a side. Are $AE$ and $CE$ altitudes?
    $endgroup$
    – Rocket Man
    Nov 6 '13 at 17:25










  • $begingroup$
    What is $E$? Is the triangle isosceles? How is $D$ defined?
    $endgroup$
    – pi37
    Nov 6 '13 at 17:36










  • $begingroup$
    The length of AD to the base BC is 10 cm
    $endgroup$
    – Roy
    Nov 6 '13 at 17:40
















$begingroup$
because you are assuming that AD is bisector, which is not given moreover AD is not perpendicular to BC, at least it is not given
$endgroup$
– newzad
Nov 6 '13 at 17:18






$begingroup$
because you are assuming that AD is bisector, which is not given moreover AD is not perpendicular to BC, at least it is not given
$endgroup$
– newzad
Nov 6 '13 at 17:18














$begingroup$
I think you need another piece of information. So far you only have an angle and a side. Are $AE$ and $CE$ altitudes?
$endgroup$
– Rocket Man
Nov 6 '13 at 17:25




$begingroup$
I think you need another piece of information. So far you only have an angle and a side. Are $AE$ and $CE$ altitudes?
$endgroup$
– Rocket Man
Nov 6 '13 at 17:25












$begingroup$
What is $E$? Is the triangle isosceles? How is $D$ defined?
$endgroup$
– pi37
Nov 6 '13 at 17:36




$begingroup$
What is $E$? Is the triangle isosceles? How is $D$ defined?
$endgroup$
– pi37
Nov 6 '13 at 17:36












$begingroup$
The length of AD to the base BC is 10 cm
$endgroup$
– Roy
Nov 6 '13 at 17:40




$begingroup$
The length of AD to the base BC is 10 cm
$endgroup$
– Roy
Nov 6 '13 at 17:40










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