There's nothing mysterious about it at all. "Frequency" simply means 
"often-ness" ... how often or how frequently something happens.
-- The frequency of traditional meals is 3 per day.
-- The frequency of an equinox is 2 per year.
-- The frequency of my sleeping really late is 1 per week.
-- The frequency of my intense desire to sleep late is 30 per month.
etc.
-- The standard unit of frequency in the SI system is "per second".
The special name for that unit is "Hertz".  (Hz)
        
                    
             
        
        
        
That only happens when the temperature is below freezing and the air around the ice is dry.
        
             
        
        
        
The aluminum foil would reflect the most light !
        
             
        
        
        
Answer:
The direction angle θ of the resultant in the Polar (positive) specification is then θ = α + 60°. The Law of Cosines is used to calculate the magnitude (r) and the Law of Sines is used to calculate the angle (α).