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

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

How do you solve 7^2=11^2+9^2-2(11)(9)cosB7^2=11^2+9^2-2(11)(9)cosB?