Review the proof. Which step contains an error?
Statement
Cos(2x) =1-2sin0)
Let 2x = .
Then x=
step 2
step 4
step 6
step 8
Step
1
cos(e) =1-2sin()
-1+ cos(e)=-2sin G)
1+cos(e) =2sin()
1-cos(e)
sin(
8
sin() =t-cos(0)

Given: ae ≅ ce ; de ≅ be prove: abcd is a parallelogram. we have that ab || dc. by a similar argument used to prove that △aeb ≅ △ced, we can show that △ ≅ △ceb by. so, ∠cad ≅ ∠ by cpctc. therefore, ad || bc by the converse of the theorem. since both pair of opposite sides are parallel, quadrilateral abcd is a parallelogram.