Question

calculate the value of A if (sinA - 1) (2CosA - 1) =0

Answer 1

It's already factored.
sin - 1 = 0
sin = 1
A = 90 ± n*360 degrees
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2cos = 1
cos = 1/2
A = 60 ± n*360 degrees
A = 300 ± n*360 degrees

Answer 2

Hope this will help you.