Question

look at the figure below. which of these triangles are obtuse triangles? select all that apply a cfd b fed c abf d bcf

Explanation:

Step1: Recall obtuse - angle definition

An obtuse - angled triangle has one angle greater than 90°.

Step2: Analyze each triangle

• In $\triangle ABF$: There is no indication of an obtuse angle.
• In $\triangle FED$: There is no indication of an obtuse angle.
• In $\triangle CFD$: $\angle FCD = 90^{\circ}$, so it is a right - triangle, not an obtuse - triangle.
• In $\triangle BCF$: $\angle BCF=90^{\circ}$, so it is a right - triangle, not an obtuse - triangle.

Since there are no obtuse - angled triangles among the given options, no options should be selected.

Answer:

None of the above (a. CFD, b. FED, c. ABF, d. BCF are not obtuse triangles)