Question

Answer 1

3:

a: \(=sin^242^0+sin^248^0+sin^243^0+sin^247^0+sin^244^0+sin^246^0+sin^245^0\)

\(=sin^242^0+cos^242^0+sin^243^0+cos^243^0+sin^244^0+cos^244^0+\dfrac{1}{2}\)

=1+1+1+1/2

=7/2

b: \(=cos^215^0+cos^275^0-cos^225^0-cos^265^0+cos^235^0+cos^255^0+cos^245^0\)

\(=cos^215^0+sin^215^0-cos^225^0-sin^225^0+cos^235^0+sin^235^0+\dfrac{1}{2}\)

=1-1+1+1/2

=3/2

c: Sửa đề: \(P=cos^21^0+cos^22^0+...+cos^288^0+cos^289^0-cos^290^0\)

\(=\left(cos^21^0+cos^289^0\right)+\left(cos^22^0+cos^288^0\right)+...+cos^245^0-0\)

\(=1+1+...+1+\dfrac{1}{2}\)

=44,5