题干

已知曲线C的极坐标方程是ρ=4cosθ.以极点为平面直角坐标系的原点,极轴为x轴的正半轴,建立平面直角坐标系,直线l的参数方程是x=1+
2
2
t
y=a+
2
2
t
是参数).
(Ⅰ)写出曲线C的普通方程;
(Ⅱ)若直线l与曲线C相交于A、B两点,且|AB|=14,求a的值.
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答案(点此获取答案解析)

解:(Ⅰ)由ρ=4cosθ得:ρ2=4ρcosθ,

∴x2+y2=4x,

即(x﹣2)2+y2=4,

所以曲线C的参数方程:x=

同类题4

根据短文内容和首字母提示,在下文空格处填入适当的词使短文完整。(每空一词)

    In a tree in a jungle, there once lived many birds. They were  h____ in their small nests(鸟巢) and sang every day. Before the rainy season arrived, all the animals in the jungle repaired their homes. The birds a____made their homes safer.

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    Soon the rain came. It was f____by thunder and lightning. All the animals and birds stayed at their homes. It kept raining for many days. One day, a monkey wet in the rain came into the jungle. He sat on a branch(树枝), shaking w____cold.

    The poor monkey tried his best to get a place, but f____. The leaves were not enough to save him from the rain."Brrr! Itis so cold!" said the monkey. The birds were watching all this. They felt sorry for the monkey,  b____there was little they could do for him. One of them said. "Brother! Our small nests are not big enough to give you shelter." Another bird said, "All ofus prepared for the rainy season. If you had, you would not be in this difficult  s____".

    "How dare you tell me what to do?" said the monkey, shouting at the "bird. The monkey  a____hit the bird's nest and threw it on the ground. The bird and her babies were helpless.

    The poor birds thought, "Fool never value(重视) good advice. It is better not to advise them ".