# How do I calculate the area of the triangle BDE? It should have two cases. When the point E is betwe

616947616 shared this question 2 years ago

How do I calculate the area of the triangle BDE? It should have two cases. When the point E is between the CDs, I have already calculated the area at this time, but when the point E is on the extension line of the CD, how should the area be determined? I have no idea.

Files: P9-2.ggb

For your registration , I think you must wait until you receive a second email .

For the aera , its depend on position of point C . See joined file .

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If you draw the triangle BDE, GeoGebra automatically shows its area in Algebra View.

If you need to calculate this area algebraically, choose a base for the triangle, (possibly the one you already know the equation of the line which contains it) and calculate its height by using the distance point-line formula

abs(a x0 +by0 +c)/sqrt(a^2 + b^2),

where the line containing the base has equation ax+by+c=0 and the point has coordinates (x0, y0).

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Okay, thank you for reminding me, it ’s just that my previous question has been submitted and has been under review. Later, I submitted the same question. Soon after, two identical questions passed almost at the same time.In addition, you said that this is not a place to solve student problems. Isn't this tool used to help solve math problems? If I can't solve the problem after using this auxiliary tool, should I be able to ask here? I don't know where to help me solve these students' math problems. Could you please recommend some suitable forums for me? Thank you.

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Bonjour ,

je pense que pour calculer l'aire , soit il manque une information soit l'aire est à déterminer en fonction d'une variable .

Un forum approprié pour les problèmes de géométrie : ici

Cordialement

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Thank you, frndmrsl，I will ask the students geometric questions in the forum you gave in the future. I hope that there will be enthusiastic people to help, thank you again.

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in your file P9-2.ggb , line l is not défined .

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Oh, sorry, g in the original picture is l, I changed it now.

In addition, after I registered an account with ici, my mailbox received an email. After opening the connection, the prompt was as follows, but after a while, the link failed, but I still ca n’t log in. What is the reason?

-------------------------------------------------------------

Merci de vous être enregistré. L'approbation d'un modérateur est nécessaire à l'activation de votre compte. Vous recevrez un courriel après qu'un modérateur ait validé vos informations.

Files: P9-2.ggb
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For your registration , I think you must wait until you receive a second email .

For the aera , its depend on position of point C . See joined file .

1

Thank you very much for your answers. Can I ask you directly for future math problems? (If you are convenient), how can I contact you and ask you math questions directly? Thanks again.

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Unfortunaly , GeoGebra does not allow to contact members .

My email is feclmarsal@yahoo.com

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I sent you an email. If you have time, check it out, mainly because I failed to register the ici forum, and it did n’t look like unsuccessful. It ’s strange that I ca n’t log in after registering, and then I use the forum mailbox to find the password , I received an email with a username and a new password, but I still ca n’t log in with the new password. What's going on?

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Quelqu'un (nous espérons vous) a demandé un nouveau mot de

passe pour votre compte sur . Si ce n'est pas vous, ignorez ce courriel

et continuez d'utiliser votre ancien mot de passe. Si c'est vous, voici

votre nouvelle identification sur le forum.

Nom d'utilisateur: 18023157850

Mot de passe: stuc118

Vous pouvez vous identifier sur à

Merci, Liste des forums

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L'adresse électronique saisie est utilisée par un utilisateur enregistré. Si vous étes cet utilisateur, identifiez vous, sinon utilisez une autre adresse électronique.

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I like to use the formula for the volume of an n-dimensional simplex. In your case:

`Area = abs((1/(2!)) Determinant(Zip({x(a), y(a), 1}, a, {B, D, E})))`