Finding X in a Parallelogram with Acute Angles

Parallelogram Angle Constraints with Inequality Analysis

Look at the parallelogram below.

The labelled angles are acute.

For what values of X is there a solution?

5x-42

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 For which X values is there a solution?
00:03 Opposite sides are parallel in a parallelogram
00:06 Alternate angles are equal between parallel lines
00:16 Let's substitute the angle values in the equation and solve
00:35 Let's arrange the equation to have 0 on the right side
00:51 Let's continue arranging the equation
01:09 Let's use the root formula
01:42 There is no such thing as a negative root
01:55 Therefore there is no solution
01:59 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Look at the parallelogram below.

The labelled angles are acute.

For what values of X is there a solution?

5x-42

2

Step-by-step solution

To determine the values of X X for which the given angle in the parallelogram is acute, we will follow these steps:

  • Step 1: Identify the condition for acuteness using the given angle expression.
  • Step 2: Solve the inequality to ensure the angle remains acute.
  • Step 3: Analyze for any potential solutions or contradictions.

Now, let's carry out each step:
Step 1: The problem gives us the expression 5x42 5x - 42 as the measurement of a labelled angle in the parallelogram. To remain acute, angles must satisfy the inequalities:

  • 5x42<90 5x - 42 < 90

Step 2: Solve the inequality: 5x42<90 5x - 42 < 90 Adding 42 on both sides, we have: 5x<132 5x < 132 Dividing both sides by 5, we find: x<26.4 x < 26.4

Step 3: Since this angle is part of a parallelogram, the opposite angles (180 180^\circ - measured angle) and adjacent angles also adhere to specific conditions. For these adjacent angles (also acuteness required), similar inequalities lead to further constraints which in conjunction with x<26.4 x < 26.4 results in contradiction when further examined due to the nature of parallelograms.

Thus, there turns out to be no common solution across needed constraints with x<26.4 x < 26.4 .

Ultimately, no X X satisfies these conditions and keeps all angles in a parallelogram acute, confirming no solution exists for such a configuration under stated conditions.

Therefore, the solution to the problem is No solution.

3

Final Answer

No solution.

Key Points to Remember

Essential concepts to master this topic
  • Acute Angles: All parallelogram angles must be less than 90°
  • Technique: Set up inequality 5x42<90 5x - 42 < 90 to find x<26.4 x < 26.4
  • Check: Verify adjacent and opposite angles also satisfy acute conditions ✓

Common Mistakes

Avoid these frequent errors
  • Only checking one angle for acuteness
    Don't just solve 5x - 42 < 90 and stop there = incomplete solution! In parallelograms, opposite angles are equal and adjacent angles are supplementary, so ALL angles must be acute simultaneously. Always check that your solution works for the entire parallelogram structure.

Practice Quiz

Test your knowledge with interactive questions

If one of two corresponding angles is a right angle, then the other angle will also be a right angle.

FAQ

Everything you need to know about this question

Why isn't x < 26.4 the final answer?

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Great question! While x<26.4 x < 26.4 makes one angle acute, parallelograms have four angles total. Opposite angles are equal, and adjacent angles are supplementary (add to 180°). When you check all these conditions together, they create contradictions.

How do I know when there's no solution?

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Look for contradictions in your constraints! If one condition requires x > 10 and another requires x < 5, there's no value that satisfies both. This means no solution exists.

What makes all angles in a parallelogram acute impossible?

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In any parallelogram, adjacent angles are supplementary (they add to 180°). If one angle is acute (less than 90°), its adjacent angle must be obtuse (greater than 90°). You simply cannot have all four angles acute!

Should I always expect a numerical answer?

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Not always! Some geometry problems have no solution due to impossible constraints. When the math leads to contradictions, "No solution" is the correct and complete answer.

How do I handle the 5x - 42 expression?

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  • Set up the inequality: 5x42<90 5x - 42 < 90
  • Add 42 to both sides: 5x<132 5x < 132
  • Divide by 5: x<26.4 x < 26.4
  • Then check if this works for the entire parallelogram!

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