Where are the x-intercepts for f(x) = −4cos(x − pi over 2) from x = 0 to x = 2π?

The function is , 

the x-intercepts of the function are the values of x, for which f(x)=0.

So we solve , where x∈[0,2π]





CosA=0, when A is , where k is an integer.

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check the unit circle, the cosine, that is the first coordinate, is 0 at 90°, that is π/2, at 270°, that is π/2*3
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thus, 

is an element of , that is



that is



this means that x is an element of:



so x is an element of



Since x can be from x=0 to x= 2π, 

then the solution set is {0, π/2, π, 3π/2, 2π}

{0, π/2, π, 3π/2, 2π}

The correct answer is -20y