How do you solve #7^2=11^2+9^2-2(11)(9)cosB#?

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Answer 1 · 2016-11-26T16:50:57

#/_B=39.4^o#

Simplifying each term in #7^2=11^2+9^2-2(11)(9)cosB#

we get #49=121+81-198cosB#

or #49=202-198cosB#

or #198cosB=202-49=153#

and #cosB=153/198=0.7727#

and using tables or scientific calculator

#/_B=cos^(-1)0.7727=39.4^o#