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A trig identity |
2010-01-24 |
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From Natalie:
hi, i need help proving the following trig identity. i cant seem to figure out how to do it.
thanks so much.
(1+sin2x)/cos2x = cos2x/(1-sin2x)
Answered by Penny Nom. |
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An altitude of the triangle intersect a side of the triangle |
2010-01-23 |
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From Sarah:
In what type of triangle does an altitude of the triangle intersect a side of
the triangle at its midpoint??
-Sarah
Answered by Walter Whiteley. |
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A sequence |
2010-01-22 |
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From brahmaji:
0 7 26 63 _ 215 342 fill the blank? find the missing number
Answered by Robert Dawson. |
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A trig problem |
2010-01-22 |
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From vinton:
ok there is a triangle labled q, p, r......the three towns p, q, r are such that the bearing of p from q is 070 degrees.
r is 10 km due east of q and pq = 5km.
(i) calculate correct to one decimal place, the distance of pr.
(ii) given that angle qpr 142 degrees, state the bearing of r from p
Answered by Penny Nom. |
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A 20% markup |
2010-01-22 |
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From barbara:
i ran across the same question using 10%, my question is this, I have $751,400, which has been marked up 20%. I want
to know the original amount prior to mark up.... can you give me the formula.?
Answered by Penny Nom. |
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Arrays |
2010-01-21 |
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From Raven:
Mary says that the greater the number of counters, the greater the number of different arrays you can form.
Give an example that shows that Mary is wrong.
Answered by Penny Nom. |
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The binomial theorem |
2010-01-21 |
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From Laura:
Using the fact that (1 + x)^4 * (1 + x)^9 = (1 + x)^13 show (4C0 * 9C4 + 4C1*9C3 + 4C2*9C2 + 4C3*9C1 + 4C4*9C0) = 13C4
Answered by Harley Weston. |
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A 4-digit phone code |
2010-01-21 |
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From pat:
my daughter can`t remember her 4-digit code to unlock her phone. she is pretty sure it starts with a 4. can you help us? my brain is locked up
Answered by Robert Dawson. |
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The volume of a silo |
2010-01-21 |
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From heather:
The height of the silo is 30ft and the face that rests against a barn is 10 ft wide. If the barn if 5 ft from the center of the silo what is the capacity of the silo?
Answered by Penny Nom. |
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Odds and evens in an n by n+1 table |
2010-01-21 |
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From Shankar:
The boxes of an n * (n+1) table ( n rows and n+1 columns) are filled with integers.
Prove that one can cross out several columns ( not all of them !) so that after this operation
all the sums of the numbers in each row will be even.
Answered by Robert Dawson. |
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A trigonometric equation |
2010-01-21 |
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From Laura:
Find the exact solution for sin4t + √3sin4t = 0 for t when (o ≤ t ≤ π
Answered by Harley Weston. |
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The roots of a cubic |
2010-01-21 |
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From Laura:
Consider the equation x^3 + 6x^2 - x = 30.
One of the roots is equal to the sum of the other two roots.
Find the values of the three roots.
Answered by Chris Fisher and Harley Weston. |
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The inradius of an icosahedron |
2010-01-21 |
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From fnavroth:
Suppose you have an equilateral triangle.
The area of the triangle is exactly 1200 square centimetres.
Now suppose you have twenty of those triangles.
It's possible to assemble those twenty triangles into a closed
three-dimensional shape, a regular polyhedron.
What would be the volume, in cubic centimetres, of the largest sphere
that could fit inside the shape?
Answered by Chris Fisher. |
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A trig identity |
2010-01-21 |
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From Alesia:
How to prove Csc(A+B) = (csc A Csc B)/ (Cot A+ Cot B)
Answered by Penny Nom. |
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The cube of an integer |
2010-01-20 |
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From Shankar:
Can the cube of an integer end with 1985 ones ?
Answered by Robert Dawson. |
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