Question

вычислите: 10sin40sin50/cos10

Answer 1

$frac{10sin40^{0}sin50^{0}}{cos10^{0}} = frac{10sin40^{0}sin(90^{0}-40^{0})}{cos10^{0}} =frac{10sin40^{0}cos40^{0}}{cos10^{0}} =frac{5sin80^{0}}{cos10^{0}} = \ frac{5sin(90^{0}-10^{0})}{cos10^{0}} = frac{5cos10^{0}}{cos10^{0}} = 5$