Question

Вычислить. (cos 15º + sin 15º)²

Answer 1

=(cos²15º+sin²15º)+2sin15ºcos15º=1+sin30º=1+1/2=1,5

Answer 2

$(cos15^\circ +sin15^\circ )^2=\underbrace {cos^215^\circ +sin^215^\circ}_{1} +\underbrace {2sin15^\circ \cdot cos15^\circ }_{sin30^\circ }=\\\\=1+sin30^\circ =1+\frac{1}{2}=1\frac{1}{2}$