# Finding length in regular pyramid

1. Jan 13, 2012

### songoku

1. The problem statement, all variables and given/known data
Regular pyramid T.ABCD has square base with side 1 cm. N is the mid-point of AB. Find the length of TN

2. Relevant equations
not sure

3. The attempt at a solution
No information given about the height of the pyramid and the length of the slant-edge, such as TA, so how can we find TN

2. Jan 13, 2012

### Mentallic

Without being given the height of the pyramid (or something equivalent, such as the slant height) then you can't place a value on the length of TN. The only way I can see going about this is to leave the answer in terms of an unknown constant, such as AT, or maybe regular pyramid means something more than just the apex of the pyramid is normal to the centre of the base.

3. Jan 13, 2012

### songoku

Not sure, but I think regular pyramid means that the apex of the pyramid is normal to the centre of the base and the base has equal side, i.e the base is square.

If I remember correctly, the answer is 1/2 √3. But I can't find it. I have provided the complete question

4. Jan 14, 2012

### Mentallic

Ahh ok then, with the answer of $$\frac{\sqrt{3}}{2}$$ that means the edges connecting to the apex are a length of 1 each, which I guess is what was also implied by the "regular" pyramid.

5. Jan 14, 2012

### songoku

Ahhh you are correct. Thanks