Posted by **Kristien** on Saturday, February 23, 2013 at 7:43pm.

Sin4A - cos4A = sin2A - cos2A

Can i just square root the left side??:O

- Trig identities:( -
**bobpursley**, Saturday, February 23, 2013 at 7:52pm
I don't think it is an identity.

let A=90 deg

sin(360)-cos(360)=0-1

sin(180)-cos(180)=0+1

The sides are not equal.

- Trig identities:( -
**Kristien**, Saturday, February 23, 2013 at 8:17pm
?? Im sorry i don't understand what u did but im sure that this is an identity we have to prove that the left side equals the right side:)

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