UNIT ONE: LESSON FOUR: Solving Problems Using Primary Trig Ratios
Method: Use the sides/angles that are given and the side/angle you want to find to choose which trig
ratio to use.
Example 1: Find the length of x.
15
a)
x
58°
b)
c)
40⁰x
x
x
48 cm
35⁰
10 cm
Example 2. Find the measure of both acute angles in the triangle below. (4 marks)
X
37
12
Y
Z
35
Recall: To SOLVE a triangle means to find all missing sides and angles. (Three items in total.)
Example 3: Sketch the triangle and solve. Round to one decimal place, where required.
ΔABC, <A=90°, <B=42°, and c=22 cm.
Example 3: Two guy wires are attached to a flag pole as shown below. Find the distance between the
two wires.
x
y
17°
43°
15 m
Solution: Let the unknown lengths along the flagpole be “x” and “y.”
Tan
=
____________
Tan
= _____________
Hw. P. 12-13 #1abc, 2cd, 3ab, 4, 5, 8, 9, 12