sin20°/sin70°=?

Across the moment 53: Happy New Year
Look up trigonometric function table:
sin20°＝0.34202
sin70°＝0.93969
sin20°／sin70°＝0.34202／0.93969＝0.363971
Good luck and goodbye

sin5ºcos25º＋sin85ºcos65º＝

sin5º=sin(90º-85º)=cos85º
cos25º=cos(90º-65º)=sin65º
∴sin5ºcos25º+sin85ºcos65º
=cos85ºsin65º+sin85ºcos65º
=sin(65º+85º)
=sin150º
=1/2

If the vector A.B satisfies / A / = 1, B = (3,4), and the angle between a and B is 45 degrees, then a becomes B

From b = (3,4), we deduce | B | = 5
According to the formula a * b = |a | * |b | * cos&
A * b = 1 * 5 * cos 45 degree = 5 times root 2 / 2

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