B ) sin² x = 1 - cos² x
sin² x + cos² x = 1 ( correct )
D ) cot² x = csc² x - 1
cos²x / sin²x = 1/sin²x - 1 = (1-sin²x) / sin²x = cos²x/sin²x
Identities are B ) and D).
Answer:

Step-by-step explanation:

Answer:
-4x+7= -21
-4x= -21-7( this positive 7 will change to negative as we take in other side )
-4x = -28
Both the negative will be cancelled
4x = 28
x = 28/4
X = 7
therefore the X value is 7