Asound wave is modeled with the equation y=1/4 cos 2pi/3theta. find the period. explain your method. find the amplitude. explain your method. what is the equation of the midline? what does it represent?and explain this. i don''t understand this at all!

Martha has a deck of cards. she has lost some of the cards, and now the deck only contains nine spades, eleven diamonds, eight clubs, and twelve hearts. martha predicts that whenever she draws a card from the deck without looking, she will draw a club one-fifth of the time. which activity would best allow martha to test her prediction? a. randomly draw a card from the box and see if it is a club. b. randomly draw a card. then, continue to draw another card until all eight clubs are drawn. c. randomly draw and replace a card 120 times. then, observe how close to 30 times a club is drawn. d. randomly draw and replace a card 100 times. then, observe how close to 20 times a club is drawn.

You buy five cds at a sale for $5.95 each. write an expression for the total cost of the cds. then use the distributive property and mental math to evaluate the expression.

Common binomial factor of 6x(3x+7)+5(3x+7)