[幫人問]


呢題應該點好
[/幫人問]

JR8753 :[幫人問]


呢題應該點好
[/幫人問]

我有[]代表angle.

let [AED]=x
[AED]=[BED](given)
[CEB]+[BED]+[DAE]=180(angles on a straight line)
[CEB]=180-2x
CE=BE(given)
[ECB]=[EBC](base angle,isos. triangle)
[ECB]=(180-[CEB])/2(angle sum of triangle)
[ECB]=[180-(180-2x)]/2
[ECB]=2x/2
[ECB]=x

"BECAUSE"(有3點果個)[AED]=[ECB]
"SO"(都係有3點果個)DE//BC(corr. angles equal)

應該係咁架啦..

樓上：洗乜咁複雜?

2DE//BC