# Thread: area of triangles 2

1. ## area of triangles 2

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

2. Originally Posted by Tessarina
a rhombus has an area of 50 cm^2 and an internal angle of size 63 degrees. Find the lenth of its sides.

... use the parallelogram area formula provided in your previous post.

3. 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,

4. Originally Posted by Tessarina
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 ...

5. could you just show me what working out you would do?

6. Try using the formula

$A = ab\sin{\theta}$.

Like Skeeter said, show us what working you have done. We are not here to do your work for you.

7. 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.

8. Originally Posted by Tessarina
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.

9. 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

what am i doing wrong?

10. Originally Posted by Tessarina
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

what am i doing wrong?
It should actually be

$a^2\sin{\theta} = 100$.

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

11. then it would be-

a^2= 100/sin63
a= 10.59

so if that is the length of one side, how do i then work out he are of the entire rhombus?

12. Originally Posted by Tessarina
then it would be-

a^2= 100/sin63
a= 10.59

so if that is the length of one side, how do i then work out he are of the entire rhombus?
Oops, it should have actually been

$a^2\sin{63^{\circ}} = 50$.

You already know the area of the rhombus, it's $50\,\textrm{cm}^2$. You're trying to find the side length, i.e. $a$.

13. I got it!
Thank you so much.

i realised then that i was looking at the wrong answer in the back of the book, thats why it wasnt making sense.

Thank you