Answer

  1. It is 1 : 1
    Solution:
    In $\triangle\text{ABC}$
    $\text{AB = AC}$
    $\therefore \angle\text{ABC} = \angle\text{ACB}$ (angles opposite to equal sides of a triangle are equal) ...(1)
    In $\triangle\text{DBC},$
    $\text{DB = DC},$
    $\therefore \angle\text{DBC} = \angle\text{DCB}$ (angles opposite to equal sides of a triangle are equal) ...(2)
    subtract 2 from 1
    $\angle\text{ABC}-\angle\text{DBC} = \angle\text{ACB}-\angle\text{DCB}$ (equals subtracted from equals gives equal)
    $= \angle\text{ABD} = \angle\text{ACD}$
    Divide both the sides by $\triangle\text{ACD}$
    $\Rightarrow\frac{\angle\text{ABD}}{\angle\text{ACD}}=1$
    $\therefore \angle\text{ABD} : \angle\text{ACD}=1:1$

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