## virtus 3 years ago In triangle ABC, CD bisects the angle BCA and D lies on side AB. Angle c = 60 degrees, AC = 8cm and BC = 6cm

1. virtus

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2. virtus

calculate the length of AB, giving your answer correct to one decimal place

3. shandelman

Are you allowed to use the law of cosines?

4. dpaInc

use the law of cosines.... \(\large (AB)^2=(AC)^2+(BC)^2-2(AC)(BC)cosC \)

5. shandelman

I'm not sure what DC has to do with anything...put there to confuse, I guess? I can't think of a better way to do solve it.

6. virtus

@dpaInc I tried to use cosine rule, but i don't think that is how you do it cause you get a whole no. as an answer and the question asks you to round off to 1 d.p Furthermore i checked the solution booklet and it says the answer is 7.2 cm

7. shandelman

...I didn't get a whole answer, but I also didn't get 7.2. Hmm...

8. shandelman

Oh, wait. Hold on.

9. shandelman

No, I did get 7.2, never mind. c^2 = 6^2 + 8^2 - 2(6)(8)cos(60)

10. virtus

oh i must have made a mistake then! THANKS

11. virtus

I get 13.8 for some reason

12. ganeshie8

put the calculator in degrees measure.. .

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