X=
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the given triangle is an equilateral triangle in which all sides and all angles are equal so,

by angle sum property of triangle

let the angles be x

then,,

x+x+x=180

3x=180

x=60°

x=60°

Step-by-step explanation:

Equilateral and Equilangular triangles always have equal angles. Since the angles of a triangle have to always add up to 180°, all of the angles of both of these triangles, including x, have to be 60; There are 3 angles in a triangle. If all the angles are equal and they must add up to 180°, then the angles must be equal to 180 if they are multiplied by 3. Because 3×60=180, All angles are 60° and therefore x=60. The lines through the sides of the triangles represent that they are equilateral triangles.

b. an equilateral triangle inscribed in a circle

step-by-step explanation:

we are given the figure of two circles having a triangle inside.

now, we know that,

"when a figure is lying inside an another figure, then the outside figure is known as circumscribed figure and the figure lying inside is referred to as the inscribed figure".

as we see that, the circles are containing the triangle completely.

thus, the circles are the circumscribed figures and the triangle is the inscribed figure.

hence, we get, 'an equilateral triangle is inscribed in a circle'.