Simplify the following, where k represents any integer: cos (2kpi-x) (-sin (2kpi-x))

a. - cosx*sinx

b. (1/2) sin (2x)

c. cos ((1/2) x) ^2

d. cos (x) ^2*sin (x) ^2

e. undefined

If 70 is decreased by 50%, what is the new amount

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