1. Objectives:
1. Use trig to solve for missing sides or
angles of a right triangle.

2. What are Significant Digits?
The “interesting” or “important” digits.
Examples:
3.14159 has six significant digits
1000 has one
1000.0 has five
0.00035 has two
1006 has four

3. Basic Rules:
All nonzero digits are significant.
All zeros between significant digits are
significant.
All zeros to the right of both the
decimal point and all non-zero
significant digits are significant.

4. Rounding
Round each # to 3 significant digits:
742,396
0.07284
231.45

5. Now Triangles!
Remember SOH-CAH-TOA ??
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6. Example 1:
Find the value of b to three significant
digits.

7. You Try!
A 20 ft ladder is leaned against a
house at an angle of 70° with the
ground. Find:
The distance from the base of the
house to the foot of the ladder.
The height reached by the ladder.
(Round to 3 significant digits)

8. Example 2:
In ΔABC, <A = 90°, a = 29 and b = 21.
Find <B to the nearest tenth of a
degree.

9. You Try!
A tower is 553 m high. An observer at
point A, 100 m from the base of the
tower, sees the top of the tower with
angle of elevation <A. Find this angle
measure to the nearest tenth of a
degree.

10. Example 3:
A triangle has side lengths 8, 8, and 4.
Find the measures of the angles to the
nearest tenth of a degree.

11. You Try!
A rhombus with perimeter 40 cm has a
70° angle. Find the lengths of its
diagonals.