How tall Giraffe!!!
1. Pick a partner!
2. Calculate the height of the giraffe using TRIG!
(what measurements do you need to take?)
3. Each group will need
•
•
•
•
A ruler
A “Clinometer” (protractor with a string)
Paper
Phone (picture)
Knight’s Charge
2/9/15
1. A damsel is in distress and is being held captive in a tower.
Her knight in shining armor is on the ground below with a
ladder. When the knight stands 15 feet from the base of
the tower and looks up at his precious damsel, the angle
of elevation to her window is 60 degrees. How long does
the ladder have to be?
2. From the foot of a building 50 feet from the base of a tree
I have to look upwards at an angle of 22° to sight the top
of a tree. From the top of a building, 150 meters above
ground level, I have to look down at an angle of
depression of 50° to look at the top of the tree.
a. How tall is the building?
b. How tall is the tree?
Solving OBLIQUE (nonright) Triangles
Law of Sines and Cosines
Remember:
• Yesterday we learned how to use trig (SOH
CAH TOA) to find missing sides and angles of
RIGHT triangles. But all triangles aren’t RIGHT.
• So…. We need another method!
Law of Sines
Example 1
Plug in values!
Cross- multiply!
Example 2
• Find the measure of angle B.
sin 𝐵 sin 112°
=
7
10
10sin 𝐵 = 7 sin 112°
Cross- multiply!
7sin 112°
sin 𝐵 =
10
𝐵=
𝑠𝑖𝑛−1
7sin 112°
10
𝐵 = 40.47°
To get rid of “sin” you must use inverse sin (𝑠𝑖𝑛−1 )!
This just means press “2nd sin” on your calcuator!
Example 3
Fire towers A and B are located 10 miles apart.
Rangers at fire tower A spots a fire at 42°, and
rangers at fire tower B spot the same fire at 64°.
How far from tower A is the fire to the nearest
tenth of a mile?
HOMEWORK
Law of Sines wkst #1-10
Quiz on SOH CAH TOA tomorrow!