91Ó°ÊÓ

Exer. \(35-40:\) Prove the property if a and \(b\) are vectors and \(m\) is a real number. $$ \mathbf{0} \cdot \mathbf{a}=0 $$

Exer. \(35-40:\) Prove the property if a and \(b\) are vectors and \(m\) is a real number. $$ (\mathbf{a}+\mathbf{b}) \cdot(\mathbf{a}-\mathbf{b})=\mathbf{a} \cdot \mathbf{a}-\mathbf{b} \cdot \mathbf{b} $$

Exer. 21-46: Express the complex number in trigonometric form with \(0 \leq \theta<2 \pi\). $$ 3+2 i $$

Approximate the area of triangle \(A B C\). $$a=20.0, \quad b=20.0, \quad c=10.0$$

Exer. 21-46: Express the complex number in trigonometric form with \(0 \leq \theta<2 \pi\). $$ -3+i $$

A triangular field has sides of lengths \(a, b\), and \(c\) (in yards). Approximate the number of acres in the field \(\left(1\right.\) acre \(\left.=4840 \mathrm{yd}^{2}\right)\) $$a=115, \quad b=140, \quad c=200$$

A triangular field has sides of lengths \(a, b\), and \(c\) (in yards). Approximate the number of acres in the field \(\left(1\right.\) acre \(\left.=4840 \mathrm{yd}^{2}\right)\) $$a=320, \quad b=350, \quad c=500$$

Exer. 21-46: Express the complex number in trigonometric form with \(0 \leq \theta<2 \pi\). $$ -4+2 i $$

Approximate the area of a parallelogram that has sides of lengths \(a\) and \(b\) (in feet) if one angle at a vertex has measure \(\boldsymbol{\theta}\). $$a=12.0, \quad b=16.0, \quad \theta=40^{\circ}$$

Exer. 21-46: Express the complex number in trigonometric form with \(0 \leq \theta<2 \pi\). $$ -5-3 i $$