so:

Cos(x) = 7^2 + 10^2 - 10^2/2(7 * 10)

cos(x) = 49/140

acos(0.35) = x

x= 69.5 degrees.

Let me know if this looks good for explaining my answer!

Thanks

StarStrike Feb 14, 2019

#1**+1 **

You kinda' have the right idea, StarStrike

Note...BA = CA = 10 m

The Law of Cosines says that

BC^2 = BA^2 + CA^2 - 2(BA)(CA) cos (x) .....so we have...

7^2 = 10^2 + 10^2 - 2(10)(10) cos (x) simplify

49 = 200 - 200 cos(x) subtract 200 from both sides

[ 49 - 200] = - 200 cos(x) divide both sides by - 200

[ 49 - 200 ] / -200 = cos (x)

To find the measure of x, use the arccos (inverse cosine)...make sure you are in "degree" mode...so we have

arccos [ ( 49 - 200) / -200 ] = x = 40.97°

CPhill Feb 14, 2019