Transcript Geometry 8-4

Warm-Up
• Find the value of x.
32
20°
x
Geometry 8-4
Angles of Elevation and Depression
Plus: 5-7 Acute, Right, or Obtuse?
Definition
• An angle of elevation is the angle formed by a
horizontal line and a line of sight to a point above
the line.
• An angle of depression is the angle formed by a
horizontal line and a line of sight to a point below
the line.
• Angles of elevation and depression are congruent
because they are alternate interior angles.
Example
• Identify each angle as an angle of
elevation or depression.
5-7 Acute, Right, or Obtuse?
• Use the Pythagorean theorem to determine
if a triangle is acute, right, or obtuse.
• If…
• a2 + b2 > c2
– Then the triangle is acute
• a2 + b2 = c2
– Then the triangle is right
• a2 + b2 < c2
– Then the triangle is obtuse
Examples
• Determine whether each triangle is acute,
right, or obtuse.
7, 5, 10
9, 26, 25
13, 12, 5