5 Why is this inequality true? $(a+b)^2\leq 2(a^2+b^2)$ 4 Prove $\sin^2\theta + \cos^2\theta = 1$ 4 Prove that the polynomial $f_n(x)=nx^{n+1}-(n+1)x^n+1$ is divisible by $(x-1)^2$ 3 Proof of the inequality $\frac{a}{b+c}+\frac{b}{a+c}+\frac{c}{a+b} \geq \frac{3}{2}$ 3 Denominator Identity Verification

### Reputation (1,445)

This user has no recent positive reputation changes

### Questions (13)

 23 Do the Taylor series of $\sin x$ and $\cos x$ depend on the identity $\sin^2 x + \cos^2 x =1$? 10 How to prove that any (integer)$^{1/n}$ that isn't an integer, is irrational? [duplicate] 7 Rational solutions for $\tan(\pi x)=y$ 5 find minimum value of $n$ that satisfies this inequality: \$4(x_1^2+x_2^2+...+x_n^2)<2(x_1+x_2+...+x_n)

### Tags (47)

 11 calculus × 6 4 complex-numbers × 2 8 algebra-precalculus × 6 3 probability × 4 8 inequality × 5 3 contest-math × 2 4 summation × 4 3 cauchy-schwarz-inequality 4 trigonometry × 3 3 divisibility

### Bookmarks (1)

 1 prove that a negative number to the power of an irrational number cannot be real