prove-that-cos-A-2-cos-B-2-cos-C-2-4-cos-pi-A-4-cos-pi-B-4-cos-pi-C-4-where-A-B-C-pi- Tinku Tara June 4, 2023 Trigonometry 0 Comments FacebookTweetPin Question Number 86540 by jagoll last updated on 29/Mar/20 provethatcos(A2)+cos(B2)+cos(C2)=4cos(π+A4)cos(π+B4)cos(π−C4)whereA+B+C=π Commented by jagoll last updated on 29/Mar/20 RHS2{2cos(π+A4)cos(π+B4)}cos(π−C4)2{cos(2π+A+B4)+cos(A−B4)}cos(π−C4)2{−sin(A+B4)+cos(A−B4)}sin(π+C4)2{cos(A−B4)sin(π+C4)−sin(A+B4)sin(π+C4)} Commented by john santu last updated on 29/Mar/20 A+B+C=π⇒B−C=π−(A+C)LHSA=π−(B+C)A2=π2−(B+C2)cos(A2)=sin(B+C2)⇒cos(B2)+cos(C2)=2cos(B+C4)cos(B−C4)sin(B+C2)=2sin(B+C4)cos(B+C4)⇒2cos(B+C4){sin(B+C4)+cos(B−C4)}2cos(π−A4){sin(π−A4)+cos(π−(A+C)4)} Commented by jagoll last updated on 29/Mar/20 sorrysirA+B+C=π Terms of Service Privacy Policy Contact: info@tinkutara.com FacebookTweetPin Post navigation Previous Previous post: Question-86541Next Next post: Question-152082 Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Comment * Name * Save my name, email, and website in this browser for the next time I comment.