Question

If cosx+cosy =3 /5 and cosx-cosy=2/7 then show that 21tan(x-y/2) +10cot(x+y/2)
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Answer 1

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Answer 2

Answer:

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✿Yøur-ᎪղՏωᎬя

➤Length of the box (l) = 1.5 m, breadth (b) = 1 m, height (h) = 1 m

Since, the box is open at top,

∴ Sheet required to make the box = total surface area of the box – area of the top

= 2 (lb + bh + lh) – lb

= 2lb + 2bh + 2lh – lb

= lb + 2bh + 2lh

= 1.5 × 1 + 2 × 1 × 1 + 2 × 1.5 × 1

= 1.5 + 2 + 3

= 6.5 sq. m.

Since the inside and outside surface of the box are to be painted.

∴ Area to be painted = 2 × Area of the box = 2 × 6.5 = 13 sq. m.

Total cost of painting = area to be painted × rate per sq. m.

= 13 × 150

= Rs 1950

∴ 6.5 sq. m. sheet of metal will be required and the cost of painting the box will be Rs 1950.

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