cos(2π−α)•secα•cos(α+
| ||
sin(α−
|
4cos6°(sin26°−cos26°) | ||
|
13iam 花朵
共回答了26个问题采纳率:80.8% 举报
(Ⅰ)由13x2-21x-10=0,即(13x+5)(x-2)=0,
解得:x=-[5/13]或x=2,
∵cosα为方程的一根,
∴cosα=-[5/13],
则f(α)=
cosα•
1
cosα•(−sinα)
cosα•(−cosα)•(−tanα)=-[1/cosα]=[13/5];
(Ⅱ)原式=
−4cos6°cos12°
3−
cos6°
sin6°=
−4cos6°cos12°sin6°
3sin6°−cos6°=
−2sin12°cos12°
2(
3
2sin6°−
1
2cos6°)=[−sin24°
2sin(6°−30°)=
−sin24°/−2sin24°]=[1/2].
点评:
本题考点: 运用诱导公式化简求值;三角函数的化简求值.
考点点评: 此题考查了运用诱导公式化简求值,以及三角函数的化简求值,熟练掌握诱导公式是解本题的关键.
1年前
1年前2个回答
你能帮帮他们吗
精彩回答
Alice could see her grandmother doing some cooking the kitchen’s glass door.
1年前
A human ______ can do some things better than a computer, for example, creating new ideas.
1年前
They often help ___________with their housework. [ ]
1年前
We should play an ________ (积极的) role in politics, both at the national and local level.
1年前
1年前