The number of ordered pair (a,b), where a,b E (-pi,pi),

satisfying cos(a-b) = 1 and cos(a + b) = 1/e ,is.......

(E means 'belongs to')

pls explain.....

cos(a+b)=1/e => a+b=+or-cosinverse(1/e)

cos(a-b)=1=>a=bORa-b=pi  the latter does not satisfy cos(a+b)=1/e

hence a=b;

Thus a=b=+OR-cosinverse(1/e)/2

Thus two ordered pairs