" E2."15times55+053=(1)/(3)" and sin "alpha+sin beta=(1)/(4)," prove that "cos(a-8)/(2)=+-(5)/(21)

If cos alpha+cos beta=(1)/(3) and sin alpha+sin beta=(1)/(4) prove that cos[(alpha-beta)/(2)]=+-((5)/(24))

If coa alpha+cos beta=(1)/(3) and sin alpha+sin beta prove that cos((alpha-beta)/(2))=+-(5)/(24)

If cos alpha+ cos beta =1/3 and sin alpha+sin beta=1/4 prove that cos[(alpha-beta)/2] =+-(5/24)

If sin alpha=4/5 and cos beta =5/13, prove that cos ((alpha-beta)/2)=8/sqrt 65.

If "tan" alpha= n tan beta and sin alpha =m sin beta prove that : cos^(2)alpha=(m^(2)-1)/(n^(2)-1)

If tan alpha= n tan beta and sin alpha= m sin beta , prove that cos^2 alpha= (m^2-1)/(n^2-1) .

If cos alpha+cos beta=1/3 and sin alpha+sin beta=1/4 ,show that tan((alpha+beta)/2)=3/4

If sin alpha-sin beta=(1)/(3) and cos beta-cos alpha=(1)/(2) show that (cot(alpha+beta))/(2)=(2)/(3)

If sin alpha + sin beta = a and cos alpha + cos beta = b, prove that : cos (alpha-beta) = 1/2 (a^2 + b^2 -2)

If sin alpha+sin beta=a and cos alpha+cos beta=b prove that :cos(alpha-beta)=(1)/(2)(a^(2)+b^(2)-2)