5. Given the equation y = (1/4) cos[(2pi/3)*theta]: 5a. For the general equation y = a cos(bx), the period is given by 2pi/b. In this equation, b = 2pi/3, so this means that 2pi/b = 2pi/(2pi/3) = 3. Therefore, the period of this equation is 3, and the cosine wave repeats itself every 3 x-units. 5b. For the general equation y = a cos(bx), the amplitude is given by a. Therefore the amplitude is a = 1/4, and this means that the cosine wave's range is from -1/4 to 1/4 for all values of x. 5c. The equation of the midline is y = 0. This represents the average value over the wave. This is determined by adding the highest and lowest values of the range and taking the average, in this case, 1/4 + (-1/4) = 0, and 0 / 2 = 0. Another way to do this is using the general equation y = a cos(bx) + c, where the midline's equation is y = c. In this case, there is no value of c in the given, implying that c = 0, and the midline is y = 0.
6. Let the horizontal distance be x. Then tan42 = h/x, and h = x tan42. Then using the Pythagorean theorem: 3280^2 = h^2 + x^2 3280^2 = x^2 (tan42)^2 + x^2 3280^2 = x^2 [(tan42)^2 + 1] x = 2437.52 Therefore, h = x tan42 = 2,194.75 ft.
It seems to me, that if you were to add the price of all three items together, then multiply by 7.5%, you'd have the answer. Remember that 7.5% = .075 ... in other words, that is the number you would multiply the sum of the items by. Does that help?
