数学T paper 2讨论专区

Lov瑜瑜4ever

The random variable Z is uniformly distributed in the interval [m,21].
If P(Z<-1)=1/7 , find the value of m.
你们找到的m等于多少？

junchung2003

回复 621# Lov瑜瑜4ever


    -14/3?

junchung2003

回复 620# nkrealman


    我找过很多习题，都是constant class width的
应该不会问不同class width 的

Lov瑜瑜4ever

回复  Lov瑜瑜4ever


    -14/3?
junchung2003 发表于 13-12-2010 09:39 PM

我也是算到这个答案。。。可是书本的答案是-1.5==

Lov瑜瑜4ever

原来是我看错题目了。。。哈哈。。。
[m,2]看成[m,21]了。。。不好意思哦。。。哈哈

Lov瑜瑜4ever

A continuous random variable X has p.d.f as follows:
f(x)=4e^-4x , x>0
     =0 , otherwise

Find the median of X.
我找到的是(1/2)(In 2)。。。
可是书本的答案是(1/4)(In 2)。。。

數學神童

Given points A,B,C and D form a rectangle and vector OA=a, OB=b, OC=c and OD=d, prove that lal^2+lcl^2=lbl^2+ldl^2

whyyie

回复 627# 數學神童

long_sign

问题又来了
show that the expression 8 cos^2 x -6 sin x cos x +2 may be expressed in the form rcos (2x+α)+s ,and determine the value of the constants r,s and α.hence ,or otherwise, find the greatest and latest values of the expression as x varies.

whyyie

回复 629# long_sign

8 cos 2x - 6 sin x cos x + 2
= 8 cos 2x - 3 (2 sin x cos x) + 2
= 8 cos 2x - 3 sin 2x + 2

Let 8 cos 2x - 3 sin 2x = r cos (2x+a)

Ivanlsy

回复 630# whyyie


是cos^2 x 不是 cos 2x.

Log

回复 629# long_sign
show that the expression 8 cos^2 x -6 sin x cos x +2 may be expressed in the form rcos (2x+α)+s ,and determine the value of the constants r,s and α.hence ,or otherwise, find the greatest and latest values of the expression as x varies.

8 cos^2 x -6 sin x cos x +2
=8 ({cos 2x +1}/2) -6 sin x cos x +2
=4 cos 2x +4 - (3)(2) sin x cos x +2
= 4 cos 2x-3 sin 2x +6
let 4 cos 2x-3 sin 2x =r cos (2x+a)
自己来吧

long_sign

回复  long_sign
show that the expression 8 cos^2 x -6 sin x cos x +2 may be expressed in the form  ...
Log 发表于 8-2-2011 10:18 PM

thank!做到了答案是r=5 ,s=6 ,alpher =36.....

邪魅

求各位帮帮忙！我的vector真的很烂！ 请问RESULTANT 和 RELATIVE VECTOR 有什么差别?
relative那里， 我每次都找不到那个角度！求教教我该怎样找！
A-VELOCITY 20kmh-1， N60E
B-VELOCITY 30KMH-1,   N45W
FIND A RELATIVE TO B!! 我就是不会找角度啊！

邪魅

还有！那个integration， 我也是不会做啊！！
4e^-4x 的 integration 要怎样做？
求STRP BY STEP 做法， 或者有FORMULA吗？

peaceboy

回复 635# 邪魅


    给你一个思考的方向，

let -4x = u

blazex

A triangle ABC is right angled at A. The angle bisector of <A meets BC at D. If BC=a,CA=b and AB =c, prove that AD=(2^(1/2) a sinB)/a+tan B

邪魅

我现在看到VECTOR就想死！从头到尾没一体会做！
triangle PQR have midpoint L,M,N at QR,RP,PQ respectively. show PL+QM+RN=O
我最竟然show到PP+1/2QQ!! 炸到！ 不好意思哦~谁可以给我个开头，教我怎样做！
还有，
a lane crosses with another lane at 60'. boy A is 300m from O, in one of the lane n boy B is 400m from O in another lane. both them runn to O simultaneously, VELOCITY A-15kmh-1 n B-12kmh-1. find closest distance btwn A n B~~
我很乱阿！！ 不知道到底要用distance 还是 velocity！ 后面要怎样找closest d 更加不会！

Lov瑜瑜4ever

A continuous random variable takes values from 0 to k.
The probability that X takes a value greater than x is mx+2 for 1</=x</=k
Determine the value of k and m.

graveword

回复 2# phtai2004


    是吗？