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Question

Question: 12. $y=38^\circ$...

y=38y=38^\circ

Answer

The statement y=38y=38^\circ is correct.

Explanation

Solution

The problem presents a geometric figure with two parallel lines and two transversals. We are given three angles: 122122^\circ, 2y2y, and 134134^\circ. The question asks to verify if y=38y=38^\circ is consistent with the given angles.

Let's label the points in the diagram to clarify the setup.
Let the top parallel line be L1L_1 and the bottom parallel line be L2L_2.
Let the left point where the transversal meets L1L_1 be AA.
Let the right point where the transversal meets L1L_1 be CC.
Let the common vertex where the angle 2y2y is located be BB.
So, the figure forms a triangle ABCABC, where the base ACAC lies on the line L1L_1, and the vertex BB lies on the line L2L_2.

Now, let's determine the interior angles of triangle ABCABC:

  1. Angle at A: The angle given at point AA is 122122^\circ. This is an exterior angle formed by the line L1L_1 and the segment ABAB. The interior angle BAC\angle BAC of the triangle is supplementary to this exterior angle.
    BAC=180122=58\angle BAC = 180^\circ - 122^\circ = 58^\circ.

  2. Angle at C: The angle given at point CC is 134134^\circ. This is an exterior angle formed by the line L1L_1 and the segment BCBC. The interior angle BCA\angle BCA of the triangle is supplementary to this exterior angle.
    BCA=180134=46\angle BCA = 180^\circ - 134^\circ = 46^\circ.

  3. Angle at B: The angle given at point BB is 2y2y. This is the interior angle ABC\angle ABC of the triangle.

Now, we use the property that the sum of interior angles in a triangle is 180180^\circ:
BAC+BCA+ABC=180\angle BAC + \angle BCA + \angle ABC = 180^\circ
Substitute the values we found:
58+46+2y=18058^\circ + 46^\circ + 2y = 180^\circ
104+2y=180104^\circ + 2y = 180^\circ

Now, solve for yy:
2y=1801042y = 180^\circ - 104^\circ
2y=762y = 76^\circ
y=762y = \frac{76^\circ}{2}
y=38y = 38^\circ

The calculated value of yy is 3838^\circ, which matches the value given in the question (y=38y=38^\circ). Therefore, the statement is consistent with the diagram.

The final answer is y=38\boxed{y=38^\circ}.

Explanation:

  1. Identify the geometric figure as a triangle with its base on one parallel line and the opposite vertex on the other parallel line.
  2. Calculate the interior angles of the triangle at the base using the supplementary angle property (180exterior angle180^\circ - \text{exterior angle}).
  3. Apply the triangle angle sum theorem (sum of interior angles is 180180^\circ).
  4. Solve the resulting equation for yy.
  5. Compare the calculated value of yy with the given value.

Answer: The statement y=38y=38^\circ is correct.