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

## Answer this Question

## Related Questions

- trigonometry - given triangle ABC with AB=7cm, BC=8cm and AC=9cm calculate 1. ...
- Geometry - Please answer at least one . PLEASE 1. Triangle XYZ has a right ...
- help math - In triangle ABC, points D,E,F are on sides BC,CA,AB respectively ...
- Math - If all of the following triangles have the same perimeter, which has the ...
- maths-urgently needed - In right angled triangle ABC angle B=90 degree and AB= ...
- Geometry - 1. The sides of a triangle have lenghts x, x+4, and 20. Specify those...
- geometry - obtuse triangle ABC with obtuse angle B. Point D on side AC such that...
- math - Let P and Q be the points on the sides AB and BC of a triangle ABC ...
- Math - Trigonometry problem: The sides AB and AC of triangle ABC are of lengths ...
- Math - In triangle ABC, points D,E,F are on sides BC,CA,AB respectively such ...