Use the Law of Cosines to find the measure of ∠A. Round to the nearest degree. a = 12, b = 5, c = 9

Use: a² = b² + c² – 2bc cos A

Solution given:

a = 12, b = 5, c = 9

We have

: a² = b² + c² – 2bc cos A

12²=5²+9²-2×5×9 cos A

12²-25-81=-90 cos A

cos A=38/-90

A=cos -1(-19/45)

A=115°

is a required answer.

to find the perimeter of the rectangle this is the expression:

x-9+x-9+3x-4+3x-4=138

if we simplify it:

8x-26=138

remember, 138 is what it all adds up to

the length is 11.5cm

the width is 57.5cm

the area is 661.25cm^2

the answers might not be correct use at own risk