A simple problem, I think...

Golytelee · **Joined:** Wed, 4 Jun 2003 05:55:34 UTC **Posts:** 1

Very rusty on how to do this, any help would be appreciated.

Given:
Triangle ABC

angle A= 90
angle B= 20
angle C= 70

Side BC = 9

How can I calculate Side AB's length with the information given?

Thanks in advance!

Mother Goose · **Posted:** Wed, 4 Jun 2003 06:11:29 UTC

Golytelee wrote:

Very rusty on how to do this, any help would be appreciated.

Given:
Triangle ABC

angle A= 90
angle B= 20
angle C= 70

Side BC = 9

How can I calculate Side AB's length with the information given?

Thanks in advance!

This is a right angled triangle, so you can use the trig ratios to solve this problem. Draw the triangle out.

Knowing that side BC is opposite from angle A (90 degree angle), that would be the hypothenuse and the longest side...

Using the 70 degree angle at C, you can use the sine ratio:
$\sin{\theta} = \frac{opposite}{hypothenuse}$

Theta would be your angle of 70 degrees. Opposite of this angle is side AB, and the hupothenuse is 9
$\sin{70} = \frac{AB}{9}\\\\ AB = \sin{70}(9)\\\\ AB = 8.46\\\\$

S.O.S. Mathematics CyberBoard

A simple problem, I think...

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