19.4 cm
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If we split the triangle in half from the vertex to the midpoint of the base, we create two right triangles with a hypotenuse of 20 cm (congruent sides of the original isosceles triangle) and one side (half of the base of the isosceles triangle) of 5 cm.
Let's denote the height of the isosceles triangle as 'h'.
According to the Pythagorean theorem, we have:
Therefore, the height of the isosceles triangle is approximately 19.4 cm when rounded to the nearest tenth.
