Trigonometry

Express 3 sin2x + 7 cos2x in the form R sin(2x + α), where R > 0 and 0 < α < . Give the values of R and α to 3 dp. Express 6 sinxcosx + 14 cos2x in the form a cos2x + b sin2x +c, where a, b and c are constants to be found. Hence, using your answer to (a), deduce the maximum value of 6sinxcosx + 14cos2x. ................
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