Identify the Triangle Type: 45-Degree Angle Classification Problem

Triangle Classification with Insufficient Information

What type of triangle appears in the drawing?

454545

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Determine which type of triangle is shown in the drawing
00:03 The sum of the angles in a triangle equals 180
00:09 Substitute in the relevant values according to the given data and proceed to solve for A
00:21 Isolate angle A
00:32 This is angle A
00:40 Supplementary angle on a line
00:45 It's impossible to know the other angles in the triangle
00:50 Therefore it cannot be determined, 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

What type of triangle appears in the drawing?

454545

2

Step-by-step solution

Since we are given an angle of 45 and an angle of 90, we will refer to the triangle and calculate the missing angle based on the theorem that the sum of angles in a triangle equals 180 degrees.

Let's call this angle alpha:

α+45+90=180 \alpha+45+90=180

α+135=180 \alpha+135=180

Let's move the sides:

α=180135 \alpha=180-135

α=45 \alpha=45

Looking at the second triangle, we notice that the angle adjacent to 90 will also be equal to 90 since it complements to 180 degrees.

Besides this, we don't have any more data, so we won't be able to calculate angles or determine the type of triangle.

3

Final Answer

It is not possible to calculate

Key Points to Remember

Essential concepts to master this topic
  • Triangle Angle Sum: All three angles in any triangle equal 180°
  • Technique: Given one 45° angle, need two more angles to classify
  • Check: Verify all given information before attempting classification ✓

Common Mistakes

Avoid these frequent errors
  • Assuming you can classify with partial information
    Don't assume triangle type from just one angle = wrong classification! One 45° angle could appear in right, acute, or obtuse triangles. Always check that you have enough information (all three angles or specific side relationships) before classifying.

Practice Quiz

Test your knowledge with interactive questions

In a right triangle, the side opposite the right angle is called....?

FAQ

Everything you need to know about this question

Why can't I determine the triangle type with just a 45° angle?

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A 45° angle can appear in different triangle types! It could be part of a 45-45-90 right triangle, or combined with other angles to make acute or obtuse triangles. You need all three angles to classify.

What information do I need to classify a triangle?

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You need either:

  • All three angle measures
  • All three side lengths
  • Specific combinations like two sides and included angle

One angle alone is never enough!

How do I know when there's insufficient information?

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Ask yourself: "Can I find all three angles or determine the triangle's shape with what I'm given?" If the answer is no, then there's insufficient information to classify the triangle.

What should I do when I can't classify the triangle?

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State clearly that "It is not possible to determine the triangle type" or "Insufficient information provided." This shows you understand the problem and mathematical reasoning!

Could this 45° angle be part of a right triangle?

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It could be, but we don't know for sure! A 45-45-90 triangle has a 45° angle, but so do other triangle types. Without more information, we cannot confirm it's a right triangle.

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