In triangle ABCABC shown below, sides ABAB and ACAC are (p−62) cm(p - 6\sqrt{2})\text{ cm} and (4−2) cm(4 - \sqrt{2})\text{ cm} respectively. Angle BAC=45∘BAC = 45^\circ.

  1. (i)

    Given that the area of the triangle ABCABC is (172−19) cm2(17\sqrt{2} - 19)\text{ cm}^2, show that p=14p = 14.

  2. (ii)

    find the perpendicular distance from BB to ACAC, leaving your answer in the form a2+ba\sqrt{2} + b.

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Worked solution

9(i)

1. Set up the equation for the area of the triangle using the formula $\frac{1}{2}ab\sin C$.

Area=12(AB)(AC)sin⁡(∠BAC)\text{Area} = \frac{1}{2}(AB)(AC)\sin(\angle BAC)
12(p−62)(4−2)sin⁡45∘=172−19\frac{1}{2}(p - 6\sqrt{2})(4 - \sqrt{2})\sin 45^\circ = 17\sqrt{2} - 19

2. Substitute the exact value of $\sin 45^\circ$ and expand the brackets.

12(p−62)(4−2)(22)=172−19\frac{1}{2}(p - 6\sqrt{2})(4 - \sqrt{2})\left(\frac{\sqrt{2}}{2}\right) = 17\sqrt{2} - 19
24(4p−p2−242+12)=172−19\frac{\sqrt{2}}{4}(4p - p\sqrt{2} - 24\sqrt{2} + 12) = 17\sqrt{2} - 19

3. Distribute $\frac{\sqrt{2}}{4}$ into the expanded expression.

4p2−2p−48+1224=172−19\frac{4p\sqrt{2} - 2p - 48 + 12\sqrt{2}}{4} = 17\sqrt{2} - 19
p2−12p−12+32=172−19p\sqrt{2} - \frac{1}{2}p - 12 + 3\sqrt{2} = 17\sqrt{2} - 19
(p+3)2−(12p+12)=172−19(p + 3)\sqrt{2} - \left(\frac{1}{2}p + 12\right) = 17\sqrt{2} - 19

4. Equate the rational or irrational parts to solve for $p$.

Comparing the coefficients of 2\sqrt{2}:
p+3=17p + 3 = 17
p=14p = 14

(Alternatively, comparing the rational parts:
−12p−12=−19  ⟹  −12p=−7  ⟹  p=14-\frac{1}{2}p - 12 = -19 \implies -\frac{1}{2}p = -7 \implies p = 14)

Answer

p=14p = 14

9(ii)

1. Express the perpendicular distance in terms of $AB$ and $\sin 45^\circ$

Let the perpendicular distance from BB to ACAC be hh.
h=ABsin⁡45∘h = AB \sin 45^\circ

2. Substitute the known values into the expression

From part (i), p=14p = 14, so AB=14−62AB = 14 - 6\sqrt{2}.
sin⁡45∘=22\sin 45^\circ = \frac{\sqrt{2}}{2}
h=(14−62)(22)h = (14 - 6\sqrt{2})\left(\frac{\sqrt{2}}{2}\right)

3. Expand and simplify the surd expression

h=1422−6(2)(2)2h = \frac{14\sqrt{2}}{2} - \frac{6(\sqrt{2})(\sqrt{2})}{2}
h=72−6(2)2h = 7\sqrt{2} - \frac{6(2)}{2}
h=72−6h = 7\sqrt{2} - 6

Answer

72−67\sqrt{2} - 6

AI analysis — may contain mistakes.

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