If the plane vector a = (3,4), B = (sin α, cos α), and a ‖ B, then cos2x=

A ‖ B, then B = TA
sinα=3/5
Cos α = plus or minus 4 / 5
Cos2x = the square of cos α - the square of sin α = 7 / 25

RELATED INFORMATIONS

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