Below is an equilateral triangle.
Calculate X.
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Below is an equilateral triangle.
Calculate X.
Since in an equilateral triangle all sides are equal and all angles are equal. It is also known that in a triangle the sum of angles is 180°, we can calculate X in the following way:
Let's divide both sides by 3:
55
In a right triangle, the side opposite the right angle is called....?
In an equilateral triangle, all sides are equal AND all angles are equal. If one angle is X+5, then all three angles must be X+5 to maintain the equilateral property.
This is the Triangle Angle Sum Theorem - the interior angles of ANY triangle always add up to exactly 180°. This works for all triangles: equilateral, isosceles, and scalene.
Double-check your algebra! The most common errors are: forgetting to distribute properly, making arithmetic mistakes, or not setting up the equation correctly with all three angles equal.
The problem gives us an algebraic expression X+5 for the angle measure. We need to solve for X first, then we can find that each angle equals .
Substitute X = 55 back into the original expression: each angle = . Check: ✓
An equilateral triangle has three equal sides and three equal angles. Since all angles equal 60°, this confirms it's equilateral (not just isosceles or scalene).
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