Bài 1:
cos a+sin a=m
=>\(\left(cosa+\sin a\right)^2=m^2\)
=>\(1+2\cdot\sin a\cdot cosa=m^2\)
=>\(2\cdot\sin a\cdot cosa=m^2-1\)
\(P=\left|cos\alpha-\sin\alpha\right|\)
\(=\sqrt{\left(cos\alpha-\sin\alpha\right)}^2=\sqrt{\left(cosa+\sin a\right)^2-4\cdot\sin a\cdot cosa}\)
\(=\sqrt{m^2-4\cdot\sin a\cdot cosa}\)
\(=\sqrt{m^2-2\left(m^2-1\right)}=\sqrt{m^2-2m^2+2}=\sqrt{2-m^2}\)
=>Chọn A
Câu 2: C
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