A triangle has side lengths of 9 in, 13 in, and 20 in. What is the measurement of this triangle’s largest angle? 29.9° 129.9° 136.2° 50.1°.

x =  129.9 degrees to the nearest tenth.

Step-by-step explanation:

The largest angle will be opposite the longest side (20 in). So by the Cosine Rule:

20^2 = 9^2 + 13^2 - 2*9*13 cos x      where x is the  largest angle.

cos x =  (20^2-0.640 - 9^2 - 13^2) / (-2*9*13)

cos x = -0.641025641

x =  129.87 degrees.

hope it you

step-by-step explanation:

sin(7pi/6 - pi/3)  

= sin(7pi/6 - 2pi/6)  

= sin(5pi/6)  

= sin(pi - pi/6)  

= sin(pi/6)  

= 1/2  

sin 7pi/6 - sin pi/3  

= sin (pi + pi/6) - sin pi/3  

= -sin pi/6 - sin pi/3  

= -1/2 - sqrt(3)/2  

= -(1+sqrt(3))2