Find the measure of angle∠A in the parallelogram to the right.

Upper BB2 y degrees2y°8 y degrees8y°x degreesx°left parenthesis 9 x minus 180 right parenthesis degrees(9x−180)°
C
D
A
mangle∠Aequals=

1 answer

In a parallelogram, opposite angles are equal, and adjacent angles are supplementary (they add up to 180 degrees). From your description, we have the following angles:

  • Angle A: \( m\angle A = y \)
  • Angle B: \( m\angle B = 2y \)
  • Angle C: \( m\angle C = 8y \)
  • Angle D: \( m\angle D = (9x - 180) \)

Given that angles A and B are adjacent, we can set up the equation:

\[ m\angle A + m\angle B = 180^\circ \]

Substituting in the expressions:

\[ y + 2y = 180^\circ \]

This simplifies to:

\[ 3y = 180^\circ \]

Solving for \( y \):

\[ y = \frac{180^\circ}{3} = 60^\circ \]

Now, we know that:

\[ m\angle A = y = 60^\circ \]

Let's also verify the angles \( 8y \) and \( (9x - 180) \):

  1. Calculate \( m\angle C \):

\[ m\angle C = 8y = 8 \times 60^\circ = 480^\circ \]

However, this angle seems incorrect for a typical parallelogram as angles should be less than \( 360^\circ \).

As we continue exploring \( m\angle D \):

To satisfy the property of parallelograms, set \( m\angle D \) equal to \( m\angle B \): \[ m\angle D = 2y = 120^\circ \]

Now, since \( m\angle D = (9x - 180) \): \[ (9x - 180) = 120^\circ \] adding \( 180 \) to both sides and solving for \( x \):

\[ 9x = 300 \] \[ x = \frac{300}{9} \approx 33.33^\circ \]

Finally, based on our established angle measure for A: \[ m\angle A = 60^\circ \]

Thus, the measure of angle \( A \) in the parallelogram is \( \boxed{60^\circ} \).