A= sin ²15 + sin ²30 + sin ²45+ sin ²60+sin ²75 B= cos ²12+cos ²23+cos ²34+cos45+cos ²56+cos ²67+cos78 09/08/2021 Bởi Peyton A= sin ²15 + sin ²30 + sin ²45+ sin ²60+sin ²75 B= cos ²12+cos ²23+cos ²34+cos45+cos ²56+cos ²67+cos78
Đáp án: A = $sin^{2}$15 + $sin^{2}$30 + $sin^{2}$45 + $sin^{2}$60 + $sin^{2}$75 ⇒ A = $cos^{2}$75 + $cos^{2}$60 + $sin^{2}$45 + $sin^{2}$60 + $sin^{2}$75 ⇒ A = 1 + 1 + $sin^{2}$45 ⇒ A = 2,5 B = $cos^{2}$12 + $cos^{2}$23 + $cos^{2}$34 + $cos^{}$45 + $cos^{2}$56 + $cos^{2}$67 + $cos^{}$78 ⇒ B = $sin^{2}$78 + $sin^{2}$67 + $sin^{2}$56 + $cos^{}$45 + $cos^{2}$56 + $cos^{2}$67 + $cos^{}$78 ⇒ B = $sin^{2}$78 + 1 + 1 + $cos^{}$45 + $cos^{}$78 ⇒ B = 3,9 Bình luận
Đáp án:
A = $sin^{2}$15 + $sin^{2}$30 + $sin^{2}$45 + $sin^{2}$60 + $sin^{2}$75
⇒ A = $cos^{2}$75 + $cos^{2}$60 + $sin^{2}$45 + $sin^{2}$60 + $sin^{2}$75
⇒ A = 1 + 1 + $sin^{2}$45
⇒ A = 2,5
B = $cos^{2}$12 + $cos^{2}$23 + $cos^{2}$34 + $cos^{}$45 + $cos^{2}$56 + $cos^{2}$67 + $cos^{}$78
⇒ B = $sin^{2}$78 + $sin^{2}$67 + $sin^{2}$56 + $cos^{}$45 + $cos^{2}$56 + $cos^{2}$67 + $cos^{}$78
⇒ B = $sin^{2}$78 + 1 + 1 + $cos^{}$45 + $cos^{}$78
⇒ B = 3,9