In the figure, AB = AC and DB = DC, find the ratio ∠ABD:∠ACD.
In the given figure,
In ΔABC,
AB = AC and DB = DC
In ΔABC,
∵ AB=AC
∴ ∠ACB=∠ABC ...(i)
(Angles opposite to equal sides)
Similarly, in ΔDBC,
DB = DC
∴∠DCB=∠DBC ...(ii)
Subtracting (ii) from (i)
∠ACB−∠DCB=∠ABC−∠DBC
⇒ ∠ACD=∠ABD
∴ Ratio ∠ABD:∠ACD=1:1