Question

What is value of cos40(1-2cos80)

Answer 1

cos40 (1-2cos80)
= cos(40)-2cos (40)cos (80)
= - 0.814181

Answer 2

According to the question
= cos 40 ( 1 - 2 cos 80 )
= cos (40) - 2 cos (40) cos (80)
= -0.814181