If `3t a n At a n B=1,` prove that `2cos(A+B)=cos(A-B)dot`

If 3tan A tan B=1, prove that 2cos(A+B)=cos(A-B)dot

If 3tan A tan B=1, prove that 2cos(A+B)=cos(A-B)

If 3tanA tanB=1 , then prove that 2cos(A+B)=cos(A-B)

If tan A=n tan B and sin A=m sin B, prove that cos^(2)A=(m^(2)-1)/(n^(2)-1)

If tan A = n tan B and sin A = m sin B, prove that : cos^(2) A = (m^(2) - 1)/(n^(2) - 1)

If cos A+sin B=m and sin A+cos B=n , prove that 2sin(A+B)=m^2+n^2-2.

If x/y=(cos A)/(cos B)t h e n(x t a n A+y t a n B)/(x+y)= cot(A+B)/2 (b) cot(A-B)/2 tan(A-B)/2 (d) tan(A+B)/2

ig sin B=(1)/(2) then prove that 3cos B-4cos^(3)B=0

lfcos A+s in B=m and s in A+cos B=n prove that 2sin(A+B)=m^(2)+n^(2)-2

If A+B+C=180, prove that cos^(2)A+cos^(2)B+cos^(2)C=1-2cos A cos B cos C