A wire 9 meters long is cut into two pieces. One piece is bent into a equilatera
ID: 3192851 • Letter: A
Question
A wire 9 meters long is cut into two pieces. One piece is bent into a equilateral triangle for a frame for a stained glass ornament, while the other piece is bent into a circle for a TV antenna. To reduce storage space, where should the wire be cut to minimize the total area of both figures? Give the length of wire used for each: For the equilateral triangle: For the circle: (for both, include units) Where should the wire be cut to maximize the total area? Again, give the length of wire used for each: For the equilateral triangle: For the circle: (for both, include units)Explanation / Answer
solution: we have l(total) = 3y + 2px = 8 A(total) = y²v3/4 + px² we have the equation 3y + 2px = 8 y = (8–2px)/3 A = y²v3/4 + px² A = [(8–2px)/3]²v3/4 + px² A = v3/36(8–2px)² + px² A = v3/9(4–px)² + px² A = v3/9(16–8px+p²x²) + px² A = (16/9)v3 – (8/9)v3px + (v3/9)p²x² + px² A = (v3/9+1)p²x² – (8/9)v3px + (16/9)v3 finding A' A' = 2(v3/9+1)p²x – (8/9)v3p = 0 2(v3/9+1)px = (8/9)v3 x = (8/9)v3 / 2(v3/9+1)p = 1.5396 / 7.492 = 0.205.......................Answer
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