the area of a square inscribed in a circle of radius 8cm:

a) 64 b)100 c)125 d)128

if the points (0,0),(1,2) and (x,y) are collinear,then

a)x=y b)2x=y c)x=2y d)2x=-y

given ABCD is a square, which is inscribed in a circle of radius 8 cm.

since the diagonals of the square subtends right angle at circumference,

 therefore the diagonals of square are the diameters of the circle.

BD=2*8=16 cm

let the sides of the square be x cm.

in the right angled triangle BCD,

thus the area of the square is


(2) the given points are (0,0),(1,2) and (x,y) .

if three points are collinear.

then

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1)

When a square is inscribed in a circle, the diagonal of a square must be equal to the diameter of circle.

Now, radius of circle, OA = 8 cm

∴ AC = 2 × radius of circle = 2 × 8 cm = 16 cm  ....... (1)

we know that diagonal AC of square

On equating (1) and (2), we get

side of square

Now, area of square = (side of square) × (side of square)

Hence, option (d) is the right answer.

2)

Area of triangle whose vertices are (x1, y1), (x2, y2) and (x3, y3)  .

Suppose the given point be A(0, 0), B(1, 2) and C(x, y).

The given points are collinear.

∴ Area of ΔABC = 0
1/2 * [0(2 - y) + 1(y - 0) + x(0 - 2)] = 0
0 + y - 2x = 0 * 2
y - 2x = 0
2x = y
Hence , option (b) is correct.

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