Question 1171764
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(i)   Take y2 = 2cos(x)   (the same as y1)



(ii) Take y2 = -2cos(x)   (opposite to y1)



(iii)  Regarding k1, k2, I do not understand their meaning,
since they are not defined in the post - and, therefore, can not answer.
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In part (iii), &nbsp;your post does not look like as a &nbsp;Math problem.



In whole, &nbsp;the problem in &nbsp;(i) &nbsp;and in &nbsp;(ii) &nbsp;is as if you want to ask, 

how many is &nbsp;1 + 1, &nbsp;or how many is &nbsp;1 - 1, &nbsp;dressing it up in different smart words.