Question

cos theta + sin theta = √2 ; cos 3 theta =?​

Answer 1

Answer:

-1/root2

Step-by-step explanation:

cos theta + sin theta =2

this is only possible when theta =45⁰

therefore cos (3*45)⁰= cos 135⁰

cos (90+theta) = -sin theta

therefore cos 135⁰ = -sin45⁰ = -1/root2

hope this helps you:)