Câu hỏi của shunnokeshi

Question

tính giá trị biểu thức C=sin²2^o+sin²4^o+...+sin²88^o

Nguyễn Minh Đăng · Accepted Answer

Ta có:

$C=sin^22^0+sin^24^0+...+sin^288^0$

$C=\left(sin^22^0+sin^288^0\right)+\left(sin^24^0+sin^286^0\right)+...+\left(sin^244^0+sin^246^0\right)$

$C=\left(sin^22^0+cos^22^0\right)+\left(sin^24^0+cos^24^0\right)+...+\left(sin^244^0+cos^244^0\right)$

$C=1+1+...+1$ $C=22$

Câu trả lời:

Ta có:

$C=sin^22^0+sin^24^0+...+sin^288^0$

$C=\left(sin^22^0+sin^288^0\right)+\left(sin^24^0+sin^286^0\right)+...+\left(sin^244^0+sin^246^0\right)$

$C=\left(sin^22^0+cos^22^0\right)+\left(sin^24^0+cos^24^0\right)+...+\left(sin^244^0+cos^244^0\right)$

$C=1+1+...+1$ $C=22$