any intermediate results obtaine s Simplity cos 4x cos 2x s

any intermediate results obtaine s. Simplity cos (4x) cos (2x) - sin (2x) sin (4x). TEST 2 0) (56 work will be marked incorrect (4 points) 6. Find sin (2B) exactly if cos -1/3 and 0 /2. Draw angle in the circle. 4 points)

Solution

5) cos(4x)cos(2x) – sin(2x)sin(4x)

Using the formula:

cos(a)cos(b) - sin(a)(sin(b) = cos(a + b)

the expression can be simplified as

cos(4x)cos(2x) - sin(2x)sin(4x) = cos(2x + 4x) = cos(6x)

6) cos = 1/3

     sin = sqrt[1 – 1/9] = sqrt(8)/3

    sin2 = 2*sin*cos = 2*[sqrt(8)/3](1/3) = 2*sqrt(8)/9