Posted by **lindsay** on Thursday, May 3, 2012 at 10:27pm.

In the triangle ABC, the sides AB and BC have lengths 7cm and 8cm respectively, and angle B is obtuse. the area of the triangle is 14 root 3 cm^2. Find

a.The size of angle B

b. The length of AC

- trigonometry -
**Reiny**, Friday, May 4, 2012 at 12:08am
formula for area of triangle

= (1/2)ab sinØ, where Ø is the contained angle of sides a and b

(1/2)(7)(8) sinØ = 14√3

sin Ø = 28√3/56 = √3/2

Ø = 60°

- trigonometry -
**Reiny**, Friday, May 4, 2012 at 12:08am
now use the cosine law to find AC

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