Math Is Fun Forum

demha

Member

Registered: 2012-11-25

Posts: 195

Supplementary and Complementary Angles

This is my Geometry lesson. I could use some help checking to see if I got them right or wrong. There are two here I do not know how to solve which I could use help with.

1. 87 - I said C
A 77
B24
C93
D47
E 31
F 48

2. 160 - I said A
A 10
B20
C30
D40
E 50
F 60

3. 68 - I said E
A 851
B295
C302
D574
E 112
F 638

4. 174 - I said D
A 3
B4
C5
D 6
E 7
F 8

5. a - Not sure how to solve, need help
A 180-a
B180/2
C 179*a
D 179+a
E 60
F pi

Find the complementary angles of the following.

6. 53 - I said F
A 90
B32
C 25
D 45
E 18
F 37

7. 12 - I said B
A 46
B78
C98
D31
E 52
F 64

8. 73.5 - I said A
A 16.5
B34.2
C29.4
D17.7
E 57.9
F 11.3

9. 23.7 - I said A
A 66.3
B70.1
C42.5
D83.9
E 54.8
F 36.2

10. a - Also not sure how to solve this one
A 90/a
Ba-90
Ca/2
D90-a
E 90-2
F a^2

---

I could also use some help understanding how to solve this. I believe I have to find the the third angle for the triangle:
a, (a + 80)

---

"The thing about quotes on the Internet is you cannot confirm their validity"
~Abraham Lincoln

Agnishom

Real Member

From: Riemann Sphere

Registered: 2011-01-29

Posts: 24,996

Website

Re: Supplementary and Complementary Angles

Complementary Angles: Pair of angles whose sum is 90[sup]o[/sup].

Supplementary Angles: Pair of angles whose sum is 180[sup]o[/sup].

Example - Find the complementary angle of 53
Let the required angle be x
Therefore, x + 53 = 90
==> x = 90 - 53 = 37
Thus, the required complementary angle of 53 is 37

Example - Find the supplementary angle of 53
Let the required angle be x
Therefore, x + 53 = 180
==> x = 180 - 53 = 127
Thus, the required supplementary angle of 53 is 127

The complimentary angle of a is 90 - a
The supplementary angle of a is 180 - a

---

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

Re: Supplementary and Complementary Angles

hi demha

I assume these are supplementary angles.

1. 87 - I said C
A 77
B24
C93
D47
E 31
F 48
correct

2. 160 - I said A
A 10
B20
C30
D40
E 50
F 60
160 + 10 is not 180

3. 68 - I said E
A 851
B295
C302
D574
E 112
F 638
correct

4. 174 - I said D
A 3
B4
C5
D 6
E 7
F 8
correct

5. a - Not sure how to solve, need help
A 180-a
B180/2
C 179*a
D 179+a
E 60
F pi
a plus something makes 180.  Which of these answers fits the something?

Find the complementary angles of the following.

6. 53 - I said F
A 90
B32
C 25
D 45
E 18
F 37
correct

7. 12 - I said B
A 46
B78
C98
D31
E 52
F 64
correct

8. 73.5 - I said A
A 16.5
B34.2
C29.4
D17.7
E 57.9
F 11.3
correct

9. 23.7 - I said A
A 66.3
B70.1
C42.5
D83.9
E 54.8
F 36.2
correct

10. a - Also not sure how to solve this one
A 90/a
Ba-90
Ca/2
D90-a
E 90-2
F a^2
Similar to Q5.  This time you want a plus something makes 90.

---

I could also use some help understanding how to solve this. I believe I have to find the the third angle for the triangle:
a, (a + 80)

Angles must add to 180.
So angle 1 plus angle 2 plus angle 3 = 180 => angle 3 = 180 -(angle 1 plus angle 2)

angle 3 = 180 - (a + a + 80)
Can you simplify the algebra from here?

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

demha

Member

Registered: 2012-11-25

Posts: 195

Re: Supplementary and Complementary Angles

Hi Bob,
I sent in my lesson and got all of them but #2 right. I sent in #2 and said the answer was B, 20. I got a 10 on my lesson!

---

"The thing about quotes on the Internet is you cannot confirm their validity"
~Abraham Lincoln

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

Re: Supplementary and Complementary Angles

OK, good news!  Thanks for letting me know. 

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob