Câu hỏi của Thư Nguyễn Ngọc Anh

Question

Tính:

a) $\cos^212+\cos^278+\cos^21+\cos^289$

b) $\sin^23+\sin^215+\sin^275+\sin^287$

c) $\sin^21+\sin^22+\sin^33+...+\sin^288+\sin^289$

Diễm Quỳnh · Accepted Answer

b) $sin^23^o+sin^215^o+sin^275^o+sin^287^o$

$=\left(sin^23^o+cos^23^o\right)+\left(sin^215^o+cos^215^o\right)$

$=1+1=2$Câu trả lời: b) $sin^23^o+sin^215^o+sin^275^o+sin^287^o$

$=\left(sin^23^o+cos^23^o\right)+\left(sin^215^o+cos^215^o\right)$

$=1+1=2$

Diễm Quỳnh · Answer

a) $cos^212^o+cos^278^o+cos^21^o+cos^289^o$

$=\left(sin^278^o+cos^278^o\right)+\left(sin^289^o+cos^289^o\right)$

$=1+1=2$Câu trả lời: a) $cos^212^o+cos^278^o+cos^21^o+cos^289^o$

$=\left(sin^278^o+cos^278^o\right)+\left(sin^289^o+cos^289^o\right)$

$=1+1=2$