A triangle had two sides of length a and b with an include angle measuring Pi/3 radians. Given that a increases by 5%, b decreases by 6% and the included angle increases by 2%, estimate the percentage increase of area of the triangle.

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- July 31st 2011, 07:06 AMRine198estimating percentage increase
A triangle had two sides of length a and b with an include angle measuring Pi/3 radians. Given that a increases by 5%, b decreases by 6% and the included angle increases by 2%, estimate the percentage increase of area of the triangle.

Thanks! - July 31st 2011, 07:16 AMe^(i*pi)Re: estimating percentage increase
The area of a triangle is

If we tidy up the constants in equation 2 we get

Divide eq3 by eq1 to isolate 1+x and then take 1 to get the answer in decimal form which will need changing to percentage - July 31st 2011, 07:27 AMRine198Re: estimating percentage increase
i divided equation 3 by eqn 1 which gave me :

A1(1+x)/A1=0.998717

but i don't get where to go from there? - July 31st 2011, 08:06 AMe^(i*pi)Re: estimating percentage increase
You can cancel A1:

- July 31st 2011, 08:20 AMRine198Re: estimating percentage increase
but that doesn't correspond to the answer give, which is 0.21%