$$\frac{\left(tan^2x\right)}{tan^2x+1}$$

$$f\left(x\right)=\frac{1}{x^4+16}$$

$$\cos\left(-x\right)\left(\sec\left(x\right)-\cos\left(x\right)\right)=\sin^2\left(x\right)$$

$$\left(0.7-9a\right)\left(0.6-5a\right)$$

$$\left(y^{-7}\right)\left(y^4\right)$$

$$\sqrt{26+28}$$

$$7a^2\left(-ab\right)$$