Toán Lớp 9: a)cos ^2 55độ .sin45 độ + sin^2 55 độ .cos45độ
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 9: a)cos ^2 55độ .sin45 độ + sin^2 55 độ .cos45độ
Comments ( 1 )
{\cos ^2}{55^0}.\sin {45^0} + {\sin ^2}{55^0}.\cos {45^0}\\
= {\cos ^2}{55^0}.\cos \left( {{{90}^0} – {{45}^0}} \right) + {\sin ^2}{55^0}.\cos {45^0}\\
= {\cos ^2}{55^0}.\cos {45^0} + {\sin ^2}{55^0}.\cos {45^0}\\
= \cos {45^0}\left( {{{\cos }^2}{{55}^0} + {{\sin }^2}{{55}^0}} \right)\\
= \cos {45^0}.1\\
= \cos {45^0}\\
= \dfrac{{\sqrt 2 }}{2}
\end{array}$