We read your photo as:

Show that BT is an altitude of triangle ABC and determine the coordinates of C, given A(p; 8), T(1; q), B(-2; -2), and the equations of lines AC and BC.

Mathematics

ScanSolve AI Answer

Answer

(5; -1)

37.5 square units37.5 \text{ square units}

Step-by-step solution

4 steps
  1. Show that p=−7p = -7 and q=2q = 2.

    Point A(p;8)A(p; 8) lies on the line ACAC with equation 4y+3x=114y + 3x = 11. Substitute x=px=p and y=8y=8 into the equation:

    4(8)+3p=114(8) + 3p = 11 32+3p=1132 + 3p = 11 3p=11−323p = 11 - 32 3p=−213p = -21 p=−7p = -7

    Point T(1;q)T(1; q) lies on the line ACAC with equation 4y+3x=114y + 3x = 11. Substitute x=1x=1 and y=qy=q into the equation:

    4q+3(1)=114q + 3(1) = 11 4q+3=114q + 3 = 11 4q=11−34q = 11 - 3 4q=84q = 8 q=2q = 2

    Thus, p=−7p = -7 and q=2q = 2.

  2. Show that BT is an altitude of △ABC\triangle ABC.

    An altitude is perpendicular to the opposite side. We need to show that BT⊥ACBT \perp AC.
    First, find the gradient of BTBT using points B(−2;−2)B(-2; -2) and T(1;2)T(1; 2):

    mBT=y2−y1x2−x1=2−(−2)1−(−2)=43m_{BT} = \frac{y_2 - y_1}{x_2 - x_1} = \frac{2 - (-2)}{1 - (-2)} = \frac{4}{3}

    Next, find the gradient of ACAC from its equation 4y+3x=114y + 3x = 11. Rearrange to y=mx+cy = mx + c form:

    4y=−3x+114y = -3x + 11 y=−34x+114y = -\frac{3}{4}x + \frac{11}{4}

    So, the gradient of ACAC is mAC=−34m_{AC} = -\frac{3}{4}.
    Now, check if BTBT and ACAC are perpendicular by multiplying their gradients:

    mBT×mAC=43×(−34)=−1m_{BT} \times m_{AC} = \frac{4}{3} \times \left(-\frac{3}{4}\right) = -1

    Since the product of their gradients is −1-1, BT⊥ACBT \perp AC. Therefore, BT is an altitude of △ABC\triangle ABC.

  3. Determine the coordinates of C.

    Point CC is the intersection of line ACAC and line BCBC.
    Equation of ACAC: 4y+3x=114y + 3x = 11 (1)
    Equation of BCBC: 7y−x=−127y - x = -12 (2)
    From equation (2), express xx in terms of yy:

    x=7y+12x = 7y + 12

    Substitute this expression for xx into equation (1):

    4y+3(7y+12)=114y + 3(7y + 12) = 11 4y+21y+36=114y + 21y + 36 = 11 25y+36=1125y + 36 = 11 25y=11−3625y = 11 - 36 25y=−2525y = -25 y=−1y = -1

    Substitute y=−1y = -1 back into the expression for xx:

    x=7(−1)+12x = 7(-1) + 12 x=−7+12x = -7 + 12 x=5x = 5

    The coordinates of C are (5;−1)\boxed{(5; -1)}.

  4. Determine the area of △ABC\triangle ABC.

    We can use the formula for the area of a triangle: Area =12×base×height= \frac{1}{2} \times \text{base} \times \text{height}. Since BTBT is an altitude to ACAC, we can use ACAC as the base and BTBT as the height.
    First, calculate the length of ACAC using points A(−7;8)A(-7; 8) and C(5;−1)C(5; -1):

    AC=(x2−x1)2+(y2−y1)2AC = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} AC=(5−(−7))2+(−1−8)2AC = \sqrt{(5 - (-7))^2 + (-1 - 8)^2} AC=(12)2+(−9)2AC = \sqrt{(12)^2 + (-9)^2} AC=144+81AC = \sqrt{144 + 81} AC=225AC = \sqrt{225} AC=15 unitsAC = 15 \text{ units}

    Next, calculate the length of BTBT using points B(−2;−2)B(-2; -2) and T(1;2)T(1; 2):

    BT=(x2−x1)2+(y2−y1)2BT = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} BT=(1−(−2))2+(2−(−2))2BT = \sqrt{(1 - (-2))^2 + (2 - (-2))^2} BT=(3)2+(4)2BT = \sqrt{(3)^2 + (4)^2} BT=9+16BT = \sqrt{9 + 16} BT=25BT = \sqrt{25} BT=5 unitsBT = 5 \text{ units}

    Now, calculate the area of △ABC\triangle ABC:

    Area=12×AC×BT\text{Area} = \frac{1}{2} \times AC \times BT Area=12×15×5\text{Area} = \frac{1}{2} \times 15 \times 5 Area=12×75\text{Area} = \frac{1}{2} \times 75 Area=37.5 square units\text{Area} = 37.5 \text{ square units}

    The area of △ABC\triangle ABC is 37.5 square units\boxed{37.5 \text{ square units}}.

Was this helpful?

Try one yourself

A new problem that tests the same skill.

Still stuck on this one?

Ask a follow-up, and the answer starts from this question.

Got a different question?Ask your own question