Math Problem Statement

This image shows right triangle A B C where C is the right angle. Line segment C D intersects side A B perpendicularly at point D to create two smaller right triangles B D C and A D C. Angle C B D measures 30 degrees and angle C A D measures 60 degrees. Side C B measures (2 times square root 3) units. Side A D measures 'x' units. [2\sqrt3] [A] [B] [C] [D] [30^\circ] [60^\circ] [x] What is the value of [x] in the figure shown?

Solution

To solve for xx, we will break the problem down step by step, focusing on the relationships within the two smaller right triangles, BDC\triangle BDC and ADC\triangle ADC, created by the perpendicular line CDCD.

Step 1: Understanding the Given Information

We are given a right triangle ABCABC, where:

  • ACB=90\angle ACB = 90^\circ
  • CBD=30\angle CBD = 30^\circ
  • CAD=60\angle CAD = 60^\circ
  • CB=23CB = 2\sqrt{3} units
  • AD=xAD = x units
  • The line segment CDCD is perpendicular to ABAB

From this setup, we know that triangle ABCABC is a right triangle, and CDCD creates two smaller right triangles.

Step 2: Using Trigonometry in BDC\triangle BDC

Since CBD=30\angle CBD = 30^\circ and BDC\triangle BDC is a right triangle, we can apply trigonometry to relate the sides.

In right triangle BDCBDC: tan(CBD)=BCBD\tan(\angle CBD) = \frac{BC}{BD} Since CBD=30\angle CBD = 30^\circ, and tan(30)=13\tan(30^\circ) = \frac{1}{\sqrt{3}}, we get: 23BD=13\frac{2\sqrt{3}}{BD} = \frac{1}{\sqrt{3}} Now, solve for BDBD: BD=23×3=6BD = 2\sqrt{3} \times \sqrt{3} = 6

Step 3: Using Trigonometry in ADC\triangle ADC

In ADC\triangle ADC, we know CAD=60\angle CAD = 60^\circ, and ADC\triangle ADC is a right triangle. We can use the fact that: tan(CAD)=ACAD\tan(\angle CAD) = \frac{AC}{AD} Since tan(60)=3\tan(60^\circ) = \sqrt{3}, we get: ACx=3\frac{AC}{x} = \sqrt{3} Thus, AC=x3AC = x \sqrt{3}

Step 4: Applying the Pythagorean Theorem in ABC\triangle ABC

Now, let's apply the Pythagorean theorem in ABC\triangle ABC to relate ABAB, ACAC, and BCBC. Since ACB=90\angle ACB = 90^\circ, we know: AB2=AC2+BC2AB^2 = AC^2 + BC^2 We already know BC=23BC = 2\sqrt{3}, so: AB2=AC2+(23)2AB^2 = AC^2 + (2\sqrt{3})^2 AB2=AC2+12AB^2 = AC^2 + 12

Next, we can express ABAB as the sum of ADAD and BDBD: AB=AD+BD=x+6AB = AD + BD = x + 6 Substitute this into the Pythagorean theorem: (x+6)2=AC2+12(x + 6)^2 = AC^2 + 12

Step 5: Substituting AC=x3AC = x \sqrt{3}

Now, substitute AC=x3AC = x\sqrt{3} into the equation: (x+6)2=(x3)2+12(x + 6)^2 = (x\sqrt{3})^2 + 12 (x+6)2=3x2+12(x + 6)^2 = 3x^2 + 12 Expanding the left side: x2+12x+36=3x2+12x^2 + 12x + 36 = 3x^2 + 12 Now, move all terms to one side: x2+12x+363x212=0x^2 + 12x + 36 - 3x^2 - 12 = 0 2x2+12x+24=0-2x^2 + 12x + 24 = 0 Divide through by -2: x26x12=0x^2 - 6x - 12 = 0

Step 6: Solving the Quadratic Equation

Now, solve the quadratic equation x26x12=0x^2 - 6x - 12 = 0 using the quadratic formula: x=(6)±(6)24(1)(12)2(1)x = \frac{-(-6) \pm \sqrt{(-6)^2 - 4(1)(-12)}}{2(1)} x=6±36+482x = \frac{6 \pm \sqrt{36 + 48}}{2} x=6±842x = \frac{6 \pm \sqrt{84}}{2} x=6±2212x = \frac{6 \pm 2\sqrt{21}}{2} x=3±21x = 3 \pm \sqrt{21}

Since xx represents a length, it must be positive. Thus, the solution is: x=3+21x = 3 + \sqrt{21}

Final Answer:

The value of xx is 3+213 + \sqrt{21} units.


Would you like further details or clarification? Here are some related questions:

  1. How does the Pythagorean theorem apply to right triangles in geometry?
  2. Can trigonometric ratios be used in any triangle, or just right triangles?
  3. What are other ways to solve quadratic equations besides the quadratic formula?
  4. How does the tangent function relate to the sides of a right triangle?
  5. How can geometric figures be decomposed into smaller triangles for easier analysis?

Tip: Remember that when solving geometric problems with trigonometry or the Pythagorean theorem, organizing your steps systematically and using known ratios and relationships can simplify the process.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Pythagorean Theorem
Quadratic Equations

Formulas

tan(30°) = 1/√3
tan(60°) = √3
Pythagorean Theorem: a^2 + b^2 = c^2
Quadratic Equation: ax^2 + bx + c = 0

Theorems

Pythagorean Theorem
Trigonometric Ratios

Suitable Grade Level

Grades 9-11