Question from chetna, a parent:

Q 1) In triangle LMN, l=7, m=5 , n=4. find ANGLE N.

After applying the rule and substituting values i'm getting Cos n= 58/40. Is there something wrong. The answer at the back of the book is 34 degrees.

Chetna,

I got

n^{2} = m^{2} + l^{2} - 2 m l cos(N) so 4^{2} = 5^{2} + 7^{2} - 2(5)(7) cos(N)

which gives

cos(N) = 58/70

and thus N = 34 degrees.

Penny