Find all rational angles in degrees whose cosine is also rational
120065
Niven’s theorem proof.
95103
A rational matrix such that $A^{2017}=I_n$
87994
Find rational points on $x^2 + y^2 = 3$ and on $x^2 + y^2 = 17$
60249
Find hypotenuse given acute angle bisectors
99012
Finding an angle in a $80^\circ$-$80^\circ$-$20^\circ$ triangle (variant involving $70^\circ$ and $60^\circ$)
74143
Simplifying and evaluating $\cot 70^\circ+4\cos 70^\circ$
116822
Finding the next rational number
89561
Find the sum of angles without trigonometry?
84893
Solutions of the equations of the degree 5 and more
146047
Proving that $\cos(2\pi/n)$ is algebraic
23238
Linear combinations of sine and cosine
43300
The degree of $\sqrt{2} + \sqrt[3]{5}$ over $\mathbb Q$
83913
Rational solutions of Pell's equation
135774
Alternating roots of $f(x) = \exp(x) \sin(x) -1$ and $\exp(x)\cos(x) +1$
82631
How to find all rational points on the elliptic curves like $y^2=x^3-2$
41073
Prove $ax^2+bx+c=0$ has no rational roots if $a,b,c$ are odd
7500
$\arctan$ of a square root as a rational multiple of $\pi$