Grade 9 Math third quarter lesson 45-45-90 right triangle theorem .pptx
1. Review
• An isosceles triangle is
a triangle with
(at least) two equal sides.
Properties :
• two sides are equal.
• two angles are equal.
2. Math 9
Chem D. Oyasan, T-I
Trigonometric Ratios of Special Angles
45-45-90 degrees Right
Triangle Theorem
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3. M9GE –Ivb–c-1
Trigonometric ratios
of special angles
- Illustrate 45∘ - 45∘ -90∘
right triangle theorem
- Find the missing
length of a 45∘ - 45∘ -
90∘ Right Triangle.
Objectives
5. 45 – 45 – 90 Triangle Theorem
In a 45∘ – 45∘ – 90∘ triangle;
Concept
the legs are congruent.
the length of the hypotenuse is
2 times the length of a leg.
∴ hypotenuse = 2 leg
8. Practice makes perfect!
Find the value of each variable used in the figures.
If your answers is not an integer, express it in simplest radical form.
Rubrics Points
Criteria 5 3 1
Content Complete and correct
answers
Complete but incorrect
answers
Incomplete and
incorrect answers
Presentation Very Accurate Partially Accurate Inaccurate
Teamwork 80% and above
participated
50% and above
participated
Below 50%
participated
Time Management Finished before the
time
Finish within the time Not able to finished
10. 45 – 45 – 90 Triangle Theorem
In a 45∘ – 45∘ – 90∘ triangle;
Concept
the legs are congruent.
the length of the hypotenuse is
2 times the length of a leg.
∴ hypotenuse = 2 leg
11. Quiz
Fig. A Fig. B Fig. C
45∘
45∘
45∘
5
5
t
x
x
30m
6ft
y
x
1. Refer to fig. A. What is the value of t?
For numbers 2-3, refer to fig. B.
2. What is the value of x?
3. If the hypotenuse is equal to 20m,
what is the value of x?
For numbers 4-5, refer to fig. C.
4. What is the value of x?
5. What is the value of y?
𝑎. 8 b. 10 c. 12 d. 6
𝑎. 10 2 b. (15 2 )/2
c. 15 2
𝑎. 5 2 b. 10 2 c. 15 2 𝑑. 10
𝑎. 6𝑓𝑡 b. 6 2 ft c. 2 d. 3
d. (30 2 )/3
12. Assignment
Let triangle ABC be a 45 -45 -90 degrees triangle
where angle C = 90 degrees. Find AB if;
1. AC = 3 2. BC = 5
