ABC is an isosceles triangle.
AD is its height.
Calculate the size of angle .
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ABC is an isosceles triangle.
AD is its height.
Calculate the size of angle .
To solve this problem, we'll apply the properties of isosceles and right triangles.
Applying the angle sum property:
Simplifying, we find:
Thus, the angle is also because is isosceles and .
Therefore, the solution to this problem is .
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Is DE side in one of the triangles?
Look carefully at the angle marking in the diagram. The purple arc shows angle ABD = 55°, which is at vertex B, not the angle CAD we need to find.
In an isosceles triangle, the height from the apex (top vertex) bisects the apex angle. This means AD splits angle BAC into two equal parts: angle BAD = angle CAD.
AD is the height of the triangle, which means it's perpendicular to the base BC. A perpendicular line always creates a 90° angle.
The angle sum property () is the most reliable method. Other approaches might work but are more complex and error-prone.
Without the isosceles property, we couldn't conclude that angle BAD = angle CAD. The height would still create right angles, but we'd need more information to find specific angle measures.
Remember: In isosceles triangles, base angles are equal and the height from apex bisects the top angle. Draw it out to visualize these relationships!
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