Answer:
Step-by-step explanation:
For Triangle ABC
AB+BC+AC=42
Given that AC=12.
To get perimert of BDC
BD+BC+DC
Given that ABC is isosceles and AC is base then AB= BC
Then from the perimeter AB and BC will share 42-12= 30
Then AB=BC=15
Since BDC is equilateral and BC is 15, then BD is 15 and DC is 15
Therefore,
perimeter of triangle BDC=BD+BC+DC
P= 15+15+15
P=45
