C choi105 Apr 2013 13 0 Korea Apr 25, 2013 #1 How to solve this question? cos x cos 20^{0 }+ sin x sin 20^{0} = square root 3/2.

MarkFL Dec 2011 2,314 916 St. Augustine, FL. Apr 25, 2013 #2 Hint: Consider using the angle sum/difference identity for cosine...

MarkFL Dec 2011 2,314 916 St. Augustine, FL. Apr 26, 2013 #4 MINOANMAN said: COS(x-20)=square root 3/2 then easy... Click to expand... You have robbed the OP of the chance to find that on their own...it is good forum etiquette NOT to come along behind someone who has offered a suggestion and essentially solve the problem. Reactions: 1 person

MINOANMAN said: COS(x-20)=square root 3/2 then easy... Click to expand... You have robbed the OP of the chance to find that on their own...it is good forum etiquette NOT to come along behind someone who has offered a suggestion and essentially solve the problem.