Help please?

enter image source here

1 Answer
Jim G.
Feb 15, 2018

#"answer d."#

Explanation:

#"calculate "angleA" and "angleB" using the "color(blue)"cosine rule"#

#"then "angleC " is the sum of these 2 angles subtracted from "180^@#

#cosA=(b^2+c^2-a^2)/(2bc)#

#color(white)(cosA)=(11^2+7^2-15^2)/(2xx11xx7)=-55/154#

#rArrangleA=cos^-1(-55/154)=110.9^@#

#cosB=(a^2+c^2-b^2)/(2ac)#

#color(white)(cosB)=(15^2+7^2-11^2)/(2xx15xx7)=153/210#

#rArrangleB=cos^-1(153/210)=43.2^@#

#rArrangleC=180-(110.9+43.2)^@=25.9^@#

Related questions
Impact of this question
485 views around the world
You can reuse this answer
Creative Commons License