Question

Which expression can be used to find measure angle R

Answer 1

cos-1(-4/14)

Explanation:

If

4.5=r

3.5=s

2=t

By law of cosines:

`r^(2)=s^(2)+t^(2) -2st cosR\\\\CosR= (r^(2) -s^(2) -t^(2) )/(-2st) \\\\R=cos^(-1) (((4.5)^(2)-3.5^(2) -2^(2) )/(-2(3.5)(2)) )\\R= cos^(-1) (-(4)/(14) )`