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Find the missing angle ACB in this triangle problem using the exterior angle theorem and the given values for angle DAB and angle ABC.

Geometry problem finding angle ACB given exterior angle DAB is 132 degrees and angle ABC is 67 degrees.

Geometry problem finding angle ACB given exterior angle DAB is 132 degrees and angle ABC is 67 degrees.

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Show Answer Key & Explanations Step-by-step solution for: Finding angle measures 1 | Khan Academy Wiki | Fandom
To find the measure of angle $\angle ACB$, we need to determine the measures of the other two angles inside triangle $ABC$ first.

Step 1: Find the measure of angle $\angle BAC$.
Points $D$, $A$, and $C$ lie on a straight line. This means that angle $\angle DAB$ and angle $\angle BAC$ form a linear pair, so they add up to $180^\circ$.

We are given:
$\angle DAB = 132^\circ$

So, we can calculate $\angle BAC$:
$$ \angle BAC = 180^\circ - 132^\circ $$
$$ \angle BAC = 48^\circ $$

Step 2: Use the sum of angles in a triangle.
The sum of the interior angles of any triangle is always $180^\circ$. For triangle $ABC$, this means:
$$ \angle ABC + \angle BAC + \angle ACB = 180^\circ $$

We know:
- $\angle ABC = 67^\circ$ (given)
- $\angle BAC = 48^\circ$ (calculated in Step 1)

Substitute these values into the equation:
$$ 67^\circ + 48^\circ + \angle ACB = 180^\circ $$

Step 3: Solve for $\angle ACB$.
First, add the known angles together:
$$ 67 + 48 = 115 $$

So, the equation becomes:
$$ 115^\circ + \angle ACB = 180^\circ $$

Now, subtract $115^\circ$ from $180^\circ$:
$$ \angle ACB = 180^\circ - 115^\circ $$
$$ \angle ACB = 65^\circ $$

Final Answer:
65°
Parent Tip: Review the logic above to help your child master the concept of triangle angle measures.
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