CDE is an equilateral triangle formed on a side CD of a square ABCD (Figure). Show that ADE
BCE.
Given, that CDE is an equilateral triangle
Then DE = EC = DC
and CDE =
DEC =
ECD = 60°
To prove: ADE
BCE
Proof :
ABCD is a square then,
AB = BC = CD = AD
A =
D =
B =
C = 90°
ADE =
ADC +
CDE = 90° + 60°
and BCE =
BCD +
DCE = 90° + 60°
Then ADE =
BCE
In ADE and
BCE
AD = BC (Given)
DE = EC (Given)
ADE =
BCE (from above)
By SAS criterion of congruence
ADE
BCE
Hence proved.
Given, CDE is an equilateral triangle
Then DE = EC = DC
and CDE =
DEC =
ECD = 60°
To prove : ADE
BCE
Proof :
ABCD is a square then,
AB = BC = CD = AD
A =
D =
B =
C = 90°
ADE =
ADC +
CDE = 90° + 60°
and BCE =
BCD +
DCE = 90° + 60°
Then ADE =
BCE
In ADE and
BCE
AD = BC (Given)
DE = EC (Given)
ADE =
BCE (from above)
By SAS criterion of congruence
ADE
BCE
Hence proved.