anonymous one year ago find m∠A.

1. anonymous

2. anonymous

plz help

3. taramgrant0543664

You can use the formula a^2=c^2+b^2-2abcosA, just put your values in for a,b and c and solve for A

4. anonymous

can you help me plug them in ... im really confused :(

5. taramgrant0543664

So a=4, b=5 and c=2

6. taramgrant0543664

4^2=(5^2)+(2^2)-2(5)(2)cosA I realized in the second portion it should have been bc not ab

7. taramgrant0543664

16=25+4-20cosA 16=29-20cosA -13=-20cosA 0.65=cosA A=? Are you able to finish that?

8. anonymous

would divide 0.64 by cosA? if it is right im not really sure how to solve it

9. taramgrant0543664

Nope you have to do the inverse of the cosine function in order to get A by itself so: $\cos ^{-1}(0.65)$

10. anonymous

ohh... i know im gonna sound kinda dumb.. but how do you do the inverse?

11. anonymous

i dont mean to sound mean but can you give me the answer i only have couple of mins left ! im on a timed quiz

12. taramgrant0543664

It's 49.46

13. anonymous

thank you so much taramgrant ! really appreciate it :) :)

14. taramgrant0543664

No problem!