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Chapter 4
D. Basic Trigonometry
Part I.D
Compute angles and lengths using such
trigonometric functions as sine, cosine,
tangent, and the Pythagorean theorem.
(Application)
Body of Knowledge I.D
THE RIGHT TRIANGLE
As shown in Figure 4.1, a right triangle has sides a (the height), b (the base), and
c (the hypotenuse). There is one 90°, or right, angle. Since the angles of a triangle
add up to 180°, the sum of the remaining two angles will equal 90°, making them
complementary angles. Here, angles A and B will sum to 90°. Because each of
these angles is less than 90°, they are also classified as acute angles. Angles that
are greater than 90° are called obtuse angles. Note that there are no obtuse angles
in a right triangle.
B
a
c
90°
C
b
A
Figure 4.1 The right triangle.
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