Question

9.if
A and B are positive acute angles and
cosA 1/7,cosB13/14
then shows that A- B = 60
​

Answer 1

Answer:

cos (A-B) = cos A.cosB + sinA.sinB

= cos A.cosB + √(1-cos^2A).√(1-cos^2B)

=(1/7)(13/14) + (√48/7)(√27/14)

=(13/98) + (36/98)

=49/98=1/2 = cos 60

Therefore A-B = 60