Question

AB=9см BC=10 AC=15 cosA? CosB? cosC?

Answer 1

Объяснение:

cosA=(AC^2+AB^2-BC^2)/2×AC×AB=

=(15^2+9^2-10^2)/2×15×9=

=(225+81-100)/270=206/270=103/135

cosB=(AB^2+BC^2-AC^2)/2×AB×BC=

=(9^2+10^2-15^2)/2×9×10=

=(81+100-225)/180= - 44/180= - 11/45

cosC=(AC^2+BC^2-AB^2)/2×AC×BC=

=(15^2+10^2-9^2)/2×15×10=

=(225+100-81)/300=244/300=61/75