Evaluate $\cos 36^\circ - \cos 72^\circ$ without the aid of a calculator
56934
How do we prove $\cos(\pi/5) - \cos(2\pi/5) = 0.5$ ?.
39752
Is there a limit of $\cos(n!)$?
142673
Evaluate $\tan^{2}(20^{\circ}) + \tan^{2}(40^{\circ}) + \tan^{2}(80^{\circ})$
74143
Simplifying and evaluating $\cot 70^\circ+4\cos 70^\circ$
130058
Evaluate $\int_0^{\pi} e^{a\cos(t)}\cos(a\sin t)dt$
42391
Calculate $\tan9^{\circ}-\tan27^{\circ}-\tan63^{\circ}+\tan81^{\circ}$
90185
Another way to evaluate $\int\frac{\cos5x+\cos4x}{1-2\cos3x}{dx}$?
44715
Exact value for $\cos 36°$
143070
If $\sin A + \cos A + \tan A + \cot A + \sec A + \csc A = 7$ then $x^2 - 44x - 36 = 0$ holds for $x=\sin 2A$
106803
How to see $\cos x \leq \exp(-x^2/2)$ on $x \in [0,\pi/2]$?
13085
Evaluate $ 1 + \frac{1}{3}\frac{1}{4}+\frac{1}{5}\frac{1}{4^2}+\frac{1}{7}\frac{1}{4^3}+\dots$
13297
Prove the following trigonometric identity without a calculator involved
143584
Trigonometric ratios for angles greater than $90^\circ$?
61119
Evaluate $\prod_{i=1}^{89} \sin (i)$
14540
Any shortcut to calculate factorial of a number (Without calculator or n to 1)?
24262
Best and shortest way to evaluate mathematical expressions
51787
Evaluate $\int \cos(3x) \sin(2x) \, dx$.