area of triangles 2

Feb 2009
63
0
a rhombus has an area of 50 cm^2 and an internal angle of size 63 degrees. Find the lenth of its sides.

please show all working out.
 

skeeter

MHF Helper
Jun 2008
16,216
6,764
North Texas
a rhombus has an area of 50 cm^2 and an internal angle of size 63 degrees. Find the lenth of its sides.

please show all working out.
... use the parallelogram area formula provided in your previous post.
 
Feb 2009
63
0
i worked out the other one, but with this one i just can't seem to get the right answer.

i think iam doing something wrong,
 

skeeter

MHF Helper
Jun 2008
16,216
6,764
North Texas
i worked out the other one, but with this one i just can't seem to get the right answer.

i think iam doing something wrong,
can't fix it if we don't know what you tried ...
 
Feb 2009
63
0
could you just show me what working out you would do?
 

Prove It

MHF Helper
Aug 2008
12,883
4,999
Try using the formula

\(\displaystyle A = ab\sin{\theta}\).


Like Skeeter said, show us what working you have done. We are not here to do your work for you.
 
Feb 2009
63
0
this is the working out i did:

A= 50cm^2

1/2 x a x c x sin63= 50

acsin63= 100


-and thats all i got to.
 

Prove It

MHF Helper
Aug 2008
12,883
4,999
this is the working out i did:

A= 50cm^2

1/2 x a x c x sin63= 50

acsin63= 100


-and thats all i got to.
You're almost there. Just remember that in a rhombus, all sides are equal.
 
Feb 2009
63
0
then do i work it out by going--
2asin63=100
2a=100/sin63
2a=112.23
a=56.11

but then if i double that to get the area of the whole rhombus i get
112.23

which is the wrong answer.
the answer is: 137.0cm^2

what am i doing wrong?
 

Prove It

MHF Helper
Aug 2008
12,883
4,999
then do i work it out by going--
2asin63=100
2a=100/sin63
2a=112.23
a=56.11

but then if i double that to get the area of the whole rhombus i get
112.23

which is the wrong answer.
the answer is: 137.0cm^2

what am i doing wrong?
It should actually be

\(\displaystyle a^2\sin{\theta} = 100\).


BTW you only halve when you are finding the area of a triangle. Since it's half of a parallelogram.