Intereting Posts

$\operatorname{func}(f)\to((x,y)\in f\to f(x)=y) $ and $\operatorname{func}(f)\to((x \in \operatorname{dom}(f) \wedge f(x)=y)\to (x,y)\in f)$
Arithmetic mean. Why does it work?
Is the notorious $n^2 + n + 41$ prime generator the last of its type?
Show that there are infinitely many positive integers $N$ that cannot be written in the form $a^n+b^n+c^n$
Height one prime ideal of arithmetical rank greater than 1
Prove that Euclidean, spherical, and hyperbolic 3-manifolds are THE only three-dimensional geometries that are both homogeneous and isotropic.
The set of all functions from $\mathbb{N} \to \{0, 1\}$ is uncountable?
If a collection of sets is a subbase for a topology $\tau_0$ and a base for a topology $\tau_1$, can we conclude $\tau_0 = \tau_1$?
Four complex numbers $z_1,z_2,z_3,z_4$ lie on a generalized circle if and only if they have a real cross ratio $\in\mathbb{R}$
Representing natural numbers as matrices by use of $\otimes$
Limit of Multivariate Probability Density Function as one or more or all variables approach positive or negative infinity
Weaker Condition than Differentiability that Implies Continuity
Why do divisions like 1/98 and 1/998 give us numbers continuously being multiplied by two each time in decimal form?
Characterization of Volumes of Lattice Cubes
What is the zero subscheme of a section

Is it possible to find the angles of a triangle if I only have its sides?

If so, how can I achieve this?

Regarding my knowledge of triangles:

Whilst I was taught trigonometry a few years ago, I cannot for the life of me remember how to do things like use SOHCAHTOA to figure out the length of a side given an angle and a side. I know it’s possible and if that were my problem I would continue searching the internet for a solution, but I gather finding an angle without knowing any of the angles is more difficult.

- Prove that $\|a\|+\|b\| + \|c\| + \|a+b+c\| \geq \|a+b\| + \|b+c\| + \|c +a\|$ in the plane.
- Triangle problem related to finding an area
- probablity of random pick up three points inside a regular triangle which form a triangle and contain the center
- Prove the inequality $\frac{a}{c+a-b}+\frac{b}{a+b-c}+\frac{c}{b+c-a}\ge{3}$
- Finding out the area of a triangle if the coordinates of the three vertices are given
- equilateral triangle; $3(a^4 + b^4 + c^4 + d^4) = (a^2 + b^2 + c^2 + d^2)^2.$

- How to find $\lim_{x\to 0} \frac{1-\cos x \sqrt{\cos 2x}}{x^2}$
- Prove $\frac{2\sec\theta +3\tan\theta+5\sin\theta-7\cos\theta+5}{2\tan\theta +3\sec\theta+5\cos\theta+7\sin\theta+8}=\frac{1-\cos\theta}{\sin\theta}$
- Proving these trigonometric sums $\sum\limits_{k=0}^{n-1}\sin\frac{2k^2\pi}{n}=\frac{\sqrt{n}}{2}\left(\cos\frac{n\pi}{2}-\sin\frac{n\pi}{2}+1\right)$
- Convergence and closed form of this infinite series?
- How to do a very long division: continued fraction for tan
- Higher Order Trigonometric Function
- Prove that $\arctan\left(\frac{2x}{1-x^2}\right)=2\arctan{x}$ for all $|x|<1$, directly from the integral definition of $\arctan$
- Prove that $\frac{1}{90} \sum_{n=1}^{90} 2n \cdot \sin((2n)^\circ) = \cot (1^{\circ})$
- Finding an unknown angle
- A trigonometric identity for special angles

Use the **Cosine Law.**

Let $\triangle ABC$ have sides $a$, $b$, and $c$. We are using the usual convention that the length of the side opposite vertex $A$ is called $a$, and so on.

Let $\theta=\angle C$. Then the Cosine Law says that

$$c^2=a^2+b^2-2ab\cos \theta.$$

Since we know $a$, $b$, and $c$, we can use the above formula to calculate $\cos\theta$. Then we can use the $\cos^{-1}$ button on the calculator to find $\theta$ to excellent accuracy.

We can use the Cosine Law three times to get the three angles. But we only need to do the calculation for two of the angles: If we have them, the third can be easily found.

- Question about the Euclidean ring definition
- Proving $\int_{0}^{\pi/2}x\sqrt{\tan{x}}\log{\sin{x}}\,\mathrm dx=-\frac{\pi\sqrt{2}}{48}(\pi^2+12\pi \log{2}+24\log^2{2}) $
- Gradients of marginal likelihood of Gaussian Process with squared exponential covariance, for learning hyper-parameters
- Why is there not a simpler way to calculate the standard deviation?
- Determine the Integral $\int_{-\infty}^{\infty} e^{-x^2} \cos(2bx)dx$
- Can a $N-1$ rectifiable set be partitioned into countably many connected pieces?
- Primitive polynomials
- How to extend this extension of tetration?
- Arithmetic on $$: is $0 \cdot \infty = 0$ the only reasonable choice?
- Given the inverse of a block matrix – Complete problem
- Cyclotomic polynomials and Galois groups
- What are the formal names of operands and results for basic operations?
- Easiest proof for $\sum_{d|n}\phi(d)=n$
- Determinant of a generalized Pascal matrix
- The value of $\sqrt{1-\sqrt{1+\sqrt{1-\sqrt{1+\cdots\sqrt{1-\sqrt{1+1}}}}}}$?