Quick Start Expectations 1.Fill in planner and HWRS HW: WS: Check-up 2 2.Get a signature on HWRS 3.On desk: journal, HWRS, LS packet, bin, calculators 4.Warm Up: back of HWRS What is the slope of the line represented by the equation What is the y-intercept of the line represented by the equation 2323 y = x Solve the equations b – 45 = 3(b -15) 3. 4(w - 6) = 3(w + 1)2. 10b – 45 = 4(b -15)

Warm-Up Solve the equations b – 45 = 4(b -15) 10b – 45 = 4b – b = 4b b -4b 6b = - 15 ÷6 ÷ 6 b = -15/6 = -5/2 = (w - 6) = 3(w + 1) 4w – 24 = 3w + 3

p. 56

Circumference = dπ = 12π = 12 x 3.14 = 37.7 inches Area = πr² = 36π = 36 x 3.14 = square inches / in.²

Height: The circle sectors have radius 6 inches, and those radii are close to the heights of the triangles that make up the parallelogram. Base: The arcs of the circle sectors together comprise the circumference of the circle. They approximate the bases of the triangles that make up the parallelogram—half on the top and half on the bottom of the parallelogram. Base and Height. In the approximation by circle sectors this means (radius)(half circumference) = (6 inches)(6π inches) = 36π square inches. They are the same since the circle has simply been cut into sectors that are reassembled to approximate the parallelogram.

The two formulas are equivalent. The approximation of parallelogram area leads to the same calculations as area of a circle suggested by the radius square exploration. The two formulas will work in the same way for circles of different radii. Since the radius of a circle is half its diameter, r=12d, regardless of the value of the radius. The arcs would be closer to straight-line segments making up bases of the triangles covering the parallelogram, and the radii would be closer to heights of those triangles.

Optimal area for fixed perimeter occurs with the circle. Hint: Remember our polygonal prisms and rice! Square, the side lengths are each 3 meters, and the area is 9m². For the circle, the diameter is 12 metersπ ≈ 3.8 meters, radius ≈1.9meters, and area ≈11.3 m².

HW: WS: Check-up 2

Brain Pop Videos Measuring Circles (3 min) Pi (2.5 min) Practice with Inequalities - WS