Question

If cosa=1/7 qnd cosb =13/14 a and b are both acute angles find a-b

Answer 1

Answer:

60°

Step-by-step explanation:

cosA=1/7

cos^2 A= 1/49

sin^2 A=1-cos^2 A

           =1-1/49

          = 48/49

taking square root on both sides

sin A= 4√3÷7

cos B=13/14

sin B=$\sqrt{1-169/196}$

sin B=3√3/14

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

cos(A-B)=$\frac{1}{7} *\frac{13}{14} +\frac{4\sqrt{3} }{7} *\frac{3\sqrt{3} }{14}$

cos(A-B)=49/7*14

cos(A-B)=1/2

cos 60°=1/2

∴A-B=60°

hope it helps....