Prove that:

cos20°cos40°cos80°=1/8

see explanation

Step-by-step explanation:

Using the double angle identity for sine

sin2x = 2sinxcosx

Consider left side

cos20°cos40°cos80°

= (2sin20°cos20°)cos40°cos80°

= (2sin40°cos40°)cos80°

= (sin80°cos80° )

= (2sin80°cos80° )

= . sin160°

= . sin(180 - 20)°

= . sin20°

= = right side , thus proven

Step-by-step explanation:

hope its helps you have a great day keep smiling be happy stay safe ☺

multiply each one by 3.14

step-by-step explanation:

i think you would have to divide the money he had saved, which is $2,000 by the time he plans on exercising which is 40 hours, and the answer you get should tell you the answer to your question.