See also the
Dr. Math FAQ:
See also the
Browse High School Trigonometry
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Volume of a tank.
- Using Sine and Tangent to Find Pi [08/01/1998]
How can I determine the sine or tangent of an angle without using a
- Using Slopes to Find the Angle between Lines [11/02/2005]
What is the formula to find the acute angle between two intersecting
- Using the Law of Cosines [8/18/1995]
Prove that, in any triangle, the sum of the squares of two sides is equal
to twice the square on half the third side plus twice the square on the
line joining the midpoint of the third side to its opposite vertex.
- Using the Law of Cosines [05/21/1998]
Given the length of three sides of a triangle, how can I find the angle
between any two of the sides?
- Using the Laws of Sine and Cosine [9/24/1995]
How do I find the sine and cosine of pi/12?
- Using Trig Identities to Simplify [7/26/1996]
How do I simplify ((sin @ - 1)/cos @) - (cos @/(sin @ -1)) ?
- Using Trigonometric Identities [05/31/1999]
How can I prove that sin(4x) = 2sin(2x) - 8sin^3(x)cosx ?
- Value of Angle DBC [1/23/1996]
Imagine a triangle ABC on which angles B and C are equal to 80...
- Vector Angles: Prove A.B = |A||B|cosA [07/13/1998]
I just finished my pre-calc class, and at the end we covered vectors...
- Verifying Trigonometric Identities [07/12/2002]
How do you verify a trigonometric identity?
- Verify the Identity [04/17/2003]
Verify the identity: (csc x)/(tan x + cot x) = cos x.
- Vertices of an Octagon [10/29/1996]
Find the coordinates of the vertices of an octagon with center (0,0) when
it is inscribed in a square.
- What Is the Length of PR? [01/01/2003]
In a circle of radius 6, a triangle PQR is drawn having QR=8 and
- What is the Longest Pole? [04/04/1999]
A metal pole L ft long is pushed on the floor from one corridor into
another corridor at a right angle...
- What is the Relation between tan and tanh? [08/25/2001]
I want to know the relation between tangent and hyperbolic tangent.
- What is Trigonometry? [8/20/1996]
What is trigonometry, and what is it used for?
- What's 'Arccos'? [06/17/2001]
I'm trying to write a program in Visual Basic 6 about the distance
calculation between two cities.
- When to Use Law of Sines or Law of Cosines [02/01/2006]
When do we use the law of sines as opposed to the law of cosines?
- Where Will the Runners Meet? [03/29/1999]
Two runners, A and B, start 90 degrees away from each other on a circular
track and run at the same speed. If Runner B decides to cut across the
track, where will they meet?
- Which Side is Longer? [1/27/1995]
You are given a quadrilateral, ABCD, with diagonal DB, angle ADC = 90,
angle DBC = 43, angle C = 91, side AD = 9, side DC = 9. Find which is
longer AB or AD.
- Why does a/SinA = b/SinB = c/SinC? [08/12/1997]
I was just playing aroung with a proof of a triangle and came across the
fact that a/SinA = b/SinB = c/SinC. Why?
- Why Radians? [12/03/1997]
Why use radians to measure angles over degrees?
- Why Use Radians instead of Degrees? [09/25/2001]
Consider Maclaurin's theorem, from which we derive the Taylor series...
- Will the Tree Hit the House? [05/18/1999]
A tree is leaning at 70 degrees, our house is 66 1/2 feet away, and the
angle from our house to the top of the tree is 40 degrees...
- X = TanX [03/21/2001]
Show that x = tanx has an infinite number of solutions.