Answer:
Mean = 78.2
Standard deviation = 5.8
Step-by-step explanation:
Mathematically z-score;
= (x-mean)/SD
From the question;
12% of test scores were above 85
Thus;
P( x > 85) = 12%
P(x > 85) = 0.12
Now let’s get the z-score that has a probability of 0.12
This can be obtained from the standard normal distribution table and it is = 1.175
Thus;
1.175 = (85 - mean)/SD
let’s call the mean a and the SD b
1.175 = (85-a)/b
1.175b = 85 - a
a = 85 - 1.175b ••••••••(i)
Secondly 8% of scores were below 70
Let’s find the z-score corresponding to this proportion;
We use the standard normal distribution table as usual;
P( x < 70) = 0.08
z-score = -1.405
Thus;
-1.405 =( 70-a)/b
-1.405b = 70-a
a = 70 + 1.405b ••••••(ii)
Equate the two a
70 + 1.405b = 85 - 1.175b
85 -70 = 1.405b + 1.175b
15 = 2.58b
b = 15/2.58
b = 5.81
a = 70 + 1.405b
a = 70 + 1.405(5.81)
a = 78.16
So mean = 78.2 and Standard deviation is 5.8
To make the equation easier so that you don't have to use fractions.
Answer:
-sinx
Step-by-step explanation:
a trig identity that is crucial to solving this problem is: sin^2 + cos^2 = 1
with knowing that, you can manipulate that and turn it into 1 - sin^2x = cos^x
so 1-sin^2x/sinx - cscx becomes cos^2x/sinx - cscx
it is also important to know that cscx is the same thing as 1/sinx
knowing this information, cscx can be replaced with 1/sinx
(cos^2x)/(sinx - 1/sinx)
now sinx and 1/sinx do not have the same denominator, so we need to multiply top and bottom of sinx by sinx; it becomes....
cos^2x
---------------------
(sin^2x - 1)/sinx
notice how in the denominator it has sin^2x-1 which is equal to -cos^2x
so now it becomes:
cos^2x
--------------
-cos^2x/sinx
because we have a fraction over a fraction, we need to flip it
cos^2x sinx
---------- * ----------------
1 - cos^2x
because the cos^2x can cancel out, it becomes 1
now the answer is -sinx
Answer:
Yes it does
Sorry I need 20 characters so 2+2=4 there you go
