Write down the Principle of Tacheometry.

STATEMENT: In a isosceles triangle, the ratio of the perpendiculars from the vertex on their bases is constant.

Let `ABC` and `AB'C'` be two isosceles triangles whose bases are `BC` and `B'C'` and their vertex is at A. If `AO` and `AO'` are perpendiculars to their respective bases, then

`(AO)/(BC)=(AO')/(B'C')=1/2*cot(alpha/2)`

        `=Constant`

    Where, `alpha =`apex angle.

STATEMENT: In a isosceles triangle, the ratio of the perpendiculars from the vertex on their bases is constant.

Let `ABC` and `AB'C'` be two isosceles triangles whose bases are `BC` and `B'C'` and their vertex is at A. If `AO` and `AO'` are perpendiculars to their respective bases, then

`(AO)/(BC)=(AO')/(B'C')=1/2*cot(alpha/2)`

        `=Constant`

    Where, `alpha =`apex angle.