A^2 - b^2 = (a - b)( a +b);
<span>cos^4x-sin^4x =( cos^2x + sin^2x )( cos^2x - sin^2x) = 1* cos2x = co2x.</span>
Answer: 20. 4, 3, 2, 1...
21. 17....
Step-by-step explanation:
Answer: It is D
Step-by-step explanation:
the anwser to this queation is D
