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Triangle ABCD in FIGURE 3 below is drawn such that A = 30°; B = 90°; DC splits C such that angle θ and angle α are formed, also DC splits AB such that x and angle β are formed. BD = 10 cm and BC = 40 cm. Determine the following: 2.1.1. θ, 2.1.2. x, 2.1.3. α, 2.1.4. β, 2.1.5. AC, 2.1.6. AD

Mathematics

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Here are the solutions for the given problems:

2.1.1 Determine θ\theta

  1. Identify the relevant right-angled triangle.

    Consider △BDC\triangle BDC. It is a right-angled triangle with ∠B=90∘\angle B = 90^\circ.
    The side opposite to θ\theta is BD=10BD = 10 cm.
    The side adjacent to θ\theta is BC=40BC = 40 cm.

  2. Use the tangent function to find θ\theta.

    tan⁡θ=oppositeadjacent=BDBC\tan \theta = \frac{\text{opposite}}{\text{adjacent}} = \frac{BD}{BC} tan⁡θ=1040\tan \theta = \frac{10}{40} tan⁡θ=14\tan \theta = \frac{1}{4}
  3. Calculate the value of θ\theta.

    θ=arctan⁡(14)\theta = \arctan\left(\frac{1}{4}\right) θ≈14.04∘\theta \approx 14.04^\circ

    The value of θ\theta is \boxed{\text{14.04^\circ}}.

    2.1.2 Determine xx

  4. Refer to the problem statement and the diagram.

    The problem states that BD=10BD = 10 cm.
    The diagram labels the length of the side BDBD as xx.

  5. State the value of xx.

    x=10 cmx = 10 \text{ cm}

    The value of xx is 10 cm\boxed{\text{10 cm}}.

    2.1.3 Determine α\alpha

  6. Find the total angle at C in the larger right-angled triangle.

    Consider △ABC\triangle ABC. It is a right-angled triangle with ∠B=90∘\angle B = 90^\circ and ∠A=30∘\angle A = 30^\circ.
    The sum of angles in a triangle is 180∘180^\circ.

    ∠BCA=180∘−∠B−∠A\angle BCA = 180^\circ - \angle B - \angle A ∠BCA=180∘−90∘−30∘\angle BCA = 180^\circ - 90^\circ - 30^\circ ∠BCA=60∘\angle BCA = 60^\circ
  7. Use the relationship between ∠BCA\angle BCA, α\alpha, and θ\theta.

    From the diagram, ∠BCA=α+θ\angle BCA = \alpha + \theta.
    We found θ≈14.04∘\theta \approx 14.04^\circ in 2.1.1.

    α=∠BCA−θ\alpha = \angle BCA - \theta α=60∘−14.036∘\alpha = 60^\circ - 14.036^\circ α≈45.96∘\alpha \approx 45.96^\circ

    The value of α\alpha is \boxed{\text{45.96^\circ}}.

    2.1.4 Determine β\beta

  8. Identify the relevant triangle and known angles.

    Consider △ADC\triangle ADC. We know ∠A=30∘\angle A = 30^\circ and ∠ACD=α≈45.96∘\angle ACD = \alpha \approx 45.96^\circ.
    The angle β\beta is ∠ADC\angle ADC.

  9. Use the sum of angles in △ADC\triangle ADC.

    The sum of angles in a triangle is 180∘180^\circ.

    ∠A+∠ACD+∠ADC=180∘\angle A + \angle ACD + \angle ADC = 180^\circ 30∘+α+β=180∘30^\circ + \alpha + \beta = 180^\circ β=180∘−30∘−α\beta = 180^\circ - 30^\circ - \alpha β=150∘−45.96∘\beta = 150^\circ - 45.96^\circ β≈104.04∘\beta \approx 104.04^\circ

    The value of β\beta is \boxed{\text{104.04^\circ}}.

    2.1.5 Determine AC

  10. Identify the relevant right-angled triangle and known values.

    Consider △ABC\triangle ABC. It is a right-angled triangle with ∠B=90∘\angle B = 90^\circ.
    We know ∠A=30∘\angle A = 30^\circ and the side opposite to it, BC=40BC = 40 cm.
    AC is the hypotenuse.

  11. Use the sine function to find AC.

    sin⁡A=oppositehypotenuse=BCAC\sin A = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{BC}{AC} sin⁡30∘=40AC\sin 30^\circ = \frac{40}{AC}
  12. Solve for AC.

    AC=40sin⁡30∘AC = \frac{40}{\sin 30^\circ} AC=400.5AC = \frac{40}{0.5} AC=80 cmAC = 80 \text{ cm}

    The length of AC is 80 cm\boxed{\text{80 cm}}.

    2.1.6 Determine AD

  13. Find the length of the entire side AB.

    Consider △ABC\triangle ABC. We know ∠A=30∘\angle A = 30^\circ, ∠B=90∘\angle B = 90^\circ, and BC=40BC = 40 cm.
    We can use the tangent function.

    tan⁡A=oppositeadjacent=BCAB\tan A = \frac{\text{opposite}}{\text{adjacent}} = \frac{BC}{AB} tan⁡30∘=40AB\tan 30^\circ = \frac{40}{AB}
  14. Solve for AB.

    AB=40tan⁡30∘AB = \frac{40}{\tan 30^\circ} AB=401/3AB = \frac{40}{1/\sqrt{3}} AB=403 cmAB = 40\sqrt{3} \text{ cm}
  15. Calculate AD.

    From the diagram, DD is a point on ABAB, so AD=AB−BDAD = AB - BD.
    We know BD=x=10BD = x = 10 cm from 2.1.2.

    AD=403−10AD = 40\sqrt{3} - 10 AD≈40(1.73205)−10AD \approx 40(1.73205) - 10 AD≈69.282−10AD \approx 69.282 - 10 AD≈59.28 cmAD \approx 59.28 \text{ cm}

    The length of AD is \boxed{\text{(40\sqrt{3} - 10) cm} \text{ or approximately *59.28 cm}}.

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