Given :

We know the identity
We use this property to simplify the left hand side
So 

we know ,
when
then

For 

Add
on both sides

Finally we add 2npi for general solution
So options C and D are correct
Answer: y=2
3y+2=6y-4
6=3y
y=2
Answer:
d
Step-by-step explanation:
cause
Answer:
Check explanation
Step-by-step explanation:
I'll give you my way of solving it and you can figure it out from there.
<CEA = <DEB due to vertical angles
AE = ED due to midpoint theorem
<CAD = <ADB due to alternating angles theorem
thus two triangles congruent due to ASA