You flip a coin 30 times, about how many times would you expect to tails to appear?

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Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b

Two years ago a man was six times as old as his daughter. in 18 years he will be twice as old as his daughter. determine their present ages.