推 XII:三角疊合 07/23 15:43
→ RAINDD:a*Cos(x)+b*Sin(x) = √(a^2+b^2)*Cos(x+θ)，θ為輔助角 07/23 20:55
→ lwhs:謝謝 07/24 14:32
一題如下
90cos(377t-120)+10cos(377t+120)
= 90 [ cos(377t)cos120 + sin(377t)sin120 ]
+ 10 [ cos(377t)cos120 - sin(377t)sin120 ]
= -45cos377t + 77.94sin377t
小弟算到這邊，但是請問下式是怎麼合併出來的?
和差化積?
= 85.44 cos(377t - 125.8)
THX~
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