If `cos theta = 3/5 and cos phi =4/5,` where `theta` and `phi` are positive acute angles, then `cos ""(theta - phi)/(2)=`

If costheta=3/5 and cosphi=4/5 , where theta and phi are positive acute angles, then cos((theta-phi)/2)=

If costheta=(3)/(5)andcosphi=(4)/(5) , where theta and phi are positive acute angles, then cos((theta-phi)/(2))=?

Statement:1 if cos theta=1/7 and cos phi = 13/14 where theta and phi both are acute angles, then the value of theta-phi is pi/3 . Statement:2 cos(pi/3)=1/2

Statement:1 if cos theta=1/7 and cos phi = 13/14 where theta and phi both are acute angles, then the value of theta-phi is pi/3 . Statement:2 cos(pi/3)=1/2

cos theta=4/5, cos phi=3/5 then cos((theta-phi)/2)=

Find cos( theta + phi) " where " theta " and " phi " are acute angles and " sin theta = 4/5 " and " sin phi = 3/5.

If 3tan theta tan phi=1, then prove that 2cos(theta+phi)+cos(theta-phi)=0

If 3 tan theta tan phi=1 , then prove that 2 cos (theta+phi)=cos (theta-phi) .

If 3 tan theta tan phi=1 , then prove that 2 cos (theta+phi)=cos (theta-phi) .

If "sin" theta=(3)/(5),cos phi=-(12)/(13) , where theta and phi both lie in second quadrant, find the value of "sin"(theta+phi) .