Math Problem Statement

Find all unknown measures in the triangle.

A right triangle, A B C. Side A C measures 8 units. Angle A measures 30 degrees. Angle C measures 90 degrees.

$m\angle B=$ °, $a=$ , $c=$

Solution

We are given a right triangle ABC\triangle ABC where:

  • C=90\angle C = 90^\circ,
  • A=30\angle A = 30^\circ,
  • The length of side AC=8AC = 8 units.

We need to find the following:

  • B\angle B,
  • The length of side aa (opposite to angle AA),
  • The length of side cc (the hypotenuse).

Step 1: Find B\angle B

Since the sum of the angles in a triangle is always 180180^\circ, we can find B\angle B as follows:

B=180AC=1803090=60\angle B = 180^\circ - \angle A - \angle C = 180^\circ - 30^\circ - 90^\circ = 60^\circ

So, mB=60m\angle B = 60^\circ.

Step 2: Use trigonometry to find side aa

We can use the sine function for angle A=30A = 30^\circ, since sin(θ)=oppositehypotenuse\sin(\theta) = \frac{\text{opposite}}{\text{hypotenuse}}. Here, the opposite side to A\angle A is side aa, and the hypotenuse is side cc.

sin(30)=ac\sin(30^\circ) = \frac{a}{c} From trigonometric values, sin(30)=12\sin(30^\circ) = \frac{1}{2}. Thus:

12=ac\frac{1}{2} = \frac{a}{c} This means: a=c2a = \frac{c}{2}

Step 3: Use trigonometry to find side cc

We know AC=8AC = 8 and angle A=30A = 30^\circ. To find side cc (the hypotenuse), we use the cosine function for angle AA:

cos(30)=ACc\cos(30^\circ) = \frac{AC}{c}

We know that cos(30)=32\cos(30^\circ) = \frac{\sqrt{3}}{2}, so:

32=8c\frac{\sqrt{3}}{2} = \frac{8}{c}

Solving for cc:

c=832=8×23=163=16339.24 unitsc = \frac{8}{\frac{\sqrt{3}}{2}} = \frac{8 \times 2}{\sqrt{3}} = \frac{16}{\sqrt{3}} = \frac{16\sqrt{3}}{3} \approx 9.24 \text{ units}

Step 4: Find side aa

Now, since a=c2a = \frac{c}{2}, we can calculate:

a=9.242=4.62 unitsa = \frac{9.24}{2} = 4.62 \text{ units}

Final Answers:

  • mB=60m\angle B = 60^\circ,
  • a=4.62a = 4.62 units,
  • c=9.24c = 9.24 units.

Would you like further details or clarifications?


Here are some related questions to explore:

  1. How can we verify the solution using the Pythagorean theorem?
  2. What other trigonometric functions could we use to solve for the sides of the triangle?
  3. How would the solution change if A\angle A were 4545^\circ?
  4. What happens if the triangle is not a right triangle? How do we solve it then?
  5. Can we use the law of sines or law of cosines for this triangle?

Tip: Always check your calculations using the Pythagorean theorem for right triangles!

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Right Triangle Properties
Angle Sum Property

Formulas

Angle Sum Property: ∠A + ∠B + ∠C = 180°
Sine Function: sin(θ) = opposite/hypotenuse
Cosine Function: cos(θ) = adjacent/hypotenuse

Theorems

Pythagorean Theorem
Basic Trigonometric Ratios

Suitable Grade Level

Grades 9-11