Unit: Trig
Note Taking Guide:
Lesson 9: Trig Vocabulary Review
Square – A quadrilateral with 4 congruent sides and 4 right angles
Rectangle – A quadrilateral with 2 pairs of congruent sides and 4 right angles
Right triangle – A triangle in which one of the interior angles is a right angle (90°)
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Each of the non-right angles in a right triangle is an acute angle
Acute Angle – An angle measuring less than 90°
Sum of the Interior angles of a Triangle - 180°
Congruent – Exactly equal in size and shape
M
Midpoint – the point halfway between two given points
Perimeter – the sum of all the lengths of the sides of a shape
Complementary Angles – Two angles whose sum is 90°
Hypotenuse – The side of a right triangle opposite the 90° angle
Leg – a side of a right triangle that is not the hypotenuse (2 of them)
Altitude – the height of a triangle. The altitude is a perpendicular line from the
vertex to the opposite side.
Area of a Triangle – ½ (base)(height)
Similar Triangles – Triangles whose corresponding angles are congruent and
whose sides are the same proportion (same shape but not necessarily the same
size)
Equilateral triangle – a triangle with 3 congruent sides and 3 congruent angles
(each measuring 60°)
Isosceles Right Triangle – a right triangle with 2 congruent sides
Opposite side - The side (leg) opposite the vertex of an acute angle
Adjacent side - The side (leg) that connects with the hypotenuse at the vertex of
the acute angle (next to the angle)
Note Taking Guide:
Lesson 9: Trig Vocabulary Review
Unit: Trig
Pythagorean Theorem -
c = length of the hypotenuse
Trigonometric Ratio – The ratio of the lengths of two sides of a right triangle
- Sine, cosine, tangent
sine of θ = sin   
length of opposite side
length of hypotenuse
cosine of θ = cos   
length of adjacent side
length of hypotenuse
tangent of θ = tan   
length of opposite side
length of adjacent side
Solve a right triangle – to determine the measures of all six parts (3 angle
measurements and 3 side measurements)
- You can do this if you know either of the following:
- 2 side lengths
or – 1 side length & 1 acute angle measure
Angle of elevation - the angle between a horizontal line and the line joining the
observer's eye to some object above the horizontal line
Angle of elevation
Angle of depression - the angle between a horizontal line and the line joining the
observer's eye to some object below the horizontal line
Angle of depression
Unit: Trig
Note Taking Guide:
Lesson 9: Trig Vocabulary Review
30-60-90 Triangle – a triangle with angles measuring 30 , 60 , and 90 . The lengths
of the hypotenuse, shorter leg, and longer leg follow the pattern: 2a, a, a 3 ,
respectively.
45-45-90 Triangle – a triangle with angles measuring 45 , 45 and 90 . The two legs
have the same length and the length of the hypotenuse is
leg.
2 times the length of a