## Chiomatn93 Group Title find the area of the triangle whose sides have the given lengths. a=1, b=2, c=2 2 years ago 2 years ago

1. amistre64

use herons formula, or find an angle with the law of cosine

2. ipm1988

@ Chiomatn use the method i gave you it is valid for all

3. Chiomatn93

is s=2.5?

4. shivam_bhalla

@Chiomatn93 , I just told you the answer few minutes back. The heron's formula

5. amistre64

|dw:1336932257283:dw| c^2 = a^2 + b^2 -2ab cos(C) c^2-a^2-b^2 ------------ = cos(C) -2ab c^2-a^2-b^2 cos^-1 (------------) = C -2ab 2^2 sinC -------- = area 2

6. Chiomatn93

that wasnt the answer... u just gave me the formula

7. shivam_bhalla

@Chiomatn93 , I am not here to give answers :(

8. shivam_bhalla

9. Chiomatn93

all i want is the steps and answer.. i already know the formula.. is s=2.5?

10. shivam_bhalla

yes

11. ipm1988

@ chiomatn93 be confident in what you are you would make mistakes I also did just keep on trying

12. shivam_bhalla

@Chiomatn93, you need a calculator, not us :P

13. eliassaab

Let $s =\frac {a+b+c}{2}=\frac 5 2\\ Area= \sqrt{ s(s-a)(s-b)(s-c)}=\frac {\sqrt{15}}{4}$

14. amistre64

if never been fond of the heron formula :)

15. Chiomatn93

im getting decimals

16. eliassaab

$\frac{\sqrt{15}}{4}\approx 0.968246$