Question

In ∆JKL, j=7.9inches, k=2 inches and l =9.8. find the measure of

Answer 1

By cosine rule,

`\cos K=(j^2+l^2-k^2)/(2jl)`

Where j = 7.9 inch, k = 2 inch and l = 9.8

`\cos K=(7.9^2+9.8^2-2^2)/(2*7.9*9.8)=(154.45)/(154.84)=0.99748`
`\begin{gathered} \cos K=0.99748 \\ K=\cos ^(-1)0.99748=4.067\approx4^o \end{gathered}`

Solution: The measure of angle K is 4 degrees