Solutions obtained by accurate drawing will not be accepted. The coordinates of points A, B and C are (−2,3)(-2,3), (2,−4)(2,-4) and (7,11)(7,11) respectively.

  1. (i)

    Find the area of triangle ABCABC.

  2. (ii)

    Given that the coordinates of point DD are (−1,−2)(-1,-2), justify whether the points AA, BB and DD are collinear.

  3. (iii)

    Find the coordinates of the foot of perpendicular from point AA to the line BCBC.

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Worked solution

10(i)

1. Apply the shoelace formula to find the area of the triangle

Area=12∣−227−23−4113∣\text{Area} = \frac{1}{2} \left| \begin{matrix} -2 & 2 & 7 & -2 \\ 3 & -4 & 11 & 3 \end{matrix} \right|

2. Evaluate the determinant to find the final area

Area=12∣((−2)(−4)+(2)(11)+(7)(3))−((3)(2)+(−4)(7)+(11)(−2))∣\text{Area} = \frac{1}{2} | ((-2)(-4) + (2)(11) + (7)(3)) - ((3)(2) + (-4)(7) + (11)(-2)) |
=12∣(8+22+21)−(6−28−22)∣= \frac{1}{2} | (8 + 22 + 21) - (6 - 28 - 22) |
=12∣51−(−44)∣= \frac{1}{2} | 51 - (-44) |
=12(95)=47.5= \frac{1}{2} (95) = 47.5

Answer

47.547.5 units2^2

10(ii)

1. Calculate the gradient of the line segment AB

Gradient of AB=−4−32−(−2)=−74AB = \frac{-4 - 3}{2 - (-2)} = -\frac{7}{4}

2. Calculate the gradient of the line segment AD

Gradient of AD=−2−3−1−(−2)=−51=−5AD = \frac{-2 - 3}{-1 - (-2)} = \frac{-5}{1} = -5

3. Compare the gradients to determine collinearity

Since the gradient of AB≠AB \neq gradient of ADAD, the points AA, BB and DD do not lie on the same straight line. Therefore, they are not collinear.

Answer

Since the gradient of ABAB is not equal to the gradient of ADAD, the points AA, BB and DD are not collinear.

10(iii)

1. Find the gradient of the line $BC$.

Gradient of BC=11−(−4)7−2=155=3BC = \frac{11 - (-4)}{7 - 2} = \frac{15}{5} = 3

2. Find the equation of the line $BC$.

y−(−4)=3(x−2)y - (-4) = 3(x - 2)
y+4=3x−6y + 4 = 3x - 6
y=3x−10y = 3x - 10

3. Find the gradient and equation of the perpendicular line from $A$ to $BC$.

Gradient of perpendicular line =−13= -\frac{1}{3}
Equation of perpendicular line passing through A(−2,3)A(-2, 3):
y−3=−13(x−(−2))y - 3 = -\frac{1}{3}(x - (-2))
3y−9=−x−23y - 9 = -x - 2
x+3y=7x + 3y = 7

4. Solve the equations simultaneously to find the coordinates of the foot of the perpendicular.

Substitute y=3x−10y = 3x - 10 into x+3y=7x + 3y = 7:
x+3(3x−10)=7x + 3(3x - 10) = 7
x+9x−30=7x + 9x - 30 = 7
10x=3710x = 37
x=3.7x = 3.7

Substitute x=3.7x = 3.7 into y=3x−10y = 3x - 10:
y=3(3.7)−10=11.1−10=1.1y = 3(3.7) - 10 = 11.1 - 10 = 1.1

The coordinates of the foot of the perpendicular are (3.7,1.1)(3.7, 1.1).

Answer

(3.7,1.1)(3.7, 1.1)

AI analysis — may contain mistakes.

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