Lesson Worksheet: Isosceles Triangle Theorems Mathematics • 11th Grade

Start Practising

In this worksheet, we will practice using the isosceles triangle theorems to find missing lengths and angles in isosceles triangles.

Q1:

Consider the following triangle.

Identify the legs of the triangle.

  • A𝐴𝐵 and 𝐴𝐶
  • B𝐴𝐵 and 𝐵𝐶
  • C𝐵𝐶 and 𝐴𝐶

Q2:

In the following triangle, 𝐴𝐵=3cm, 𝐵𝐶=3cm, and 𝐴𝐶=4cm.

Identify the base angles of this triangle.

  • A∠𝐴 and ∠𝐶
  • B∠𝐴 and ∠𝐵
  • C∠𝐶 and ∠𝐵

Q3:

Find 𝑚∠𝐵𝐴𝐶.

Q4:

Find 𝑚∠𝐶𝐵𝐴 and 𝑚∠𝐷𝐴𝐶.

  • A𝑚∠𝐶𝐵𝐴=109∘, 𝑚∠𝐷𝐴𝐶=38∘
  • B𝑚∠𝐶𝐵𝐴=109∘, 𝑚∠𝐷𝐴𝐶=71∘
  • C𝑚∠𝐶𝐵𝐴=71∘, 𝑚∠𝐷𝐴𝐶=11∘
  • D𝑚∠𝐶𝐵𝐴=49∘, 𝑚∠𝐷𝐴𝐶=71∘

Q5:

Find the measures of the angles of △𝐴𝐵𝐶.

  • A𝑚∠𝐴𝐵𝐶=39.5∘, 𝑚∠𝐵𝐴𝐶=39.5∘, 𝑚∠𝐴𝐶𝐵=101∘
  • B𝑚∠𝐴𝐵𝐶=19.75∘, 𝑚∠𝐵𝐴𝐶=140.5∘, 𝑚∠𝐴𝐶𝐵=19.75∘
  • C𝑚∠𝐴𝐵𝐶=50.5∘, 𝑚∠𝐵𝐴𝐶=50.5∘, 𝑚∠𝐴𝐶𝐵=79∘
  • D𝑚∠𝐴𝐵𝐶=70.25∘, 𝑚∠𝐵𝐴𝐶=70.25∘, 𝑚∠𝐴𝐶𝐵=39.5∘

Q6:

Which pair of segments have the same length?

  • A𝐴𝐵, 𝐵𝐶
  • B𝐴𝐶, 𝐵𝐶
  • C𝐴𝐵, 𝐴𝐶

Q7:

Given that 𝑚∠𝐹𝐶𝐴=134∘ in the figure below, two sides are equal, which are these?

  • A𝐴𝐵, 𝐵𝐶
  • B𝐴𝐶, 𝐵𝐶
  • C𝐴𝐵, 𝐴𝐶
  • D𝐷𝐸, 𝐶𝐹

Q8:

In the figure, find 𝐴𝐷 given that 𝐵𝐸=6cm and 𝐴𝐸=6cm.

Q9:

Is 𝑀𝐵𝐶 an isosceles triangle?

  • ANo
  • BYes

Q10:

Is the triangle 𝐴𝐵𝐶 isosceles?

  • AYes
  • BNo

Practice Means Progress

Download the Nagwa Practice app to access 87 additional questions for this lesson!

scan me!

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.