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A diagram consisting of more than one triangle
is said to be a composite
figure.
For trigonometric problems involving a composite
figure, first decide
whether to use sine, cosine
or tangent, and then calculate the required
length or angle.
Example 17
In the given diagram, find:
a. x
b. y
Solution:
Using a Construction Line
To solve some trigonometric problems, we need to convert the given
triangle into two
right-angled triangles by drawing a perpendicular construction line
from the vertex to the opposite side.
Example 18
Find BC in the given diagram, rounded to 2 decimal places.
Solution:
Draw BD perpendicular to AC. Let BD =
x cm, BC = y cm.
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