# Week 18 Blog Post Top 5 things I have learned in Precalc 11

1：How to use Sine(two sides are known) and Cosine formula(three sides are known)

2: Arithmetic sequence was about common difference, while geometric was about common ratio

3: When being asked for angle,  we need to press shift on the calculator first

4: When  we simplify the radical, we need to find the greatest common denominator

5: When solving the equation, we need to check carefully and plug the answers into the primary formula because some of the answers does not fit the formula.

# Week 17 blog post

The things i learned this week:

Cos= adja over hypo, Cos= x/r

Sin=oppo over hypo, sin=y/r

# Week 16 Blog Post

This week I learned: when you simplify the expression, you need to find the non-permissible value first and divide the numerators and denominators by their common factors. And then multiply the numerators, multiply the denominators.

For example: $\frac{c}{10} \div \frac{5d}{2c}$

=$latex \frac{5dc}{20c} =$latex \frac{4}{d}

the non-permissible value is c/=0

# Week 15 Blog

Adding and Subtracting Rational Expressions with Monomial Denominators $\frac{2}{3} \div \frac{3}{4}$

Firstly, their common denominator is 12 because 3 times 4=12, so that means we need both times 3 or four for each side just for reaching the common denominator 12. $\frac{6}{12} \div \frac{9}{12}$

so the answer is 2 over 3.

# Week 14 Blog

Things i learned this week: when we solve rational expressions, we need to find their common denominator.

For example: $\frac{$latex x^2$+2 over}{ $x^2$ -x-6 over } { $x^2$ -x-6 over } can be factored into $x^2$-x-6=0 (x-3)(x+2)=o x=3, x=-2 if we found the common denominator,then we can factor it, that’s the way how we solved this kind of equation. # Week 13 Blog Post This week we learned chapter 8: Absolute Value and Reciprocal Functions 1: Write each absolute value function in piecewise notation a) Y=|2x-7| there are two possibilities: 2x-7>=0 or -(2x-7)<0 2x>=7 divided by 2 x<7divided by 2 the answer is : y={2x-7>=0, x >=3.5 {-(2x-7)<0,x<3.5 # Week 12 blog post Things I learned this week: There is one thing that I always will misunderstanding it, is that: solid line represents the sign is >= or<=, however, the broken line means the sign is < or >. This is one of the most important part while drawing the equation. And also, after drawing the line, we should check the sign again to make sure the shaowded part is correct and fits the sign. # Week 10 blog post For the quadratic function y=-3( $x-2^2$) + 5 ask for y-intercept, for y-intercept, means x=0, in this quadratic function made x-2=0, so y-intercept = -3* $-2^2$ + 5=-7 I’ve always messed the vertex and the intercepts, I thought y in the vertex means y-intercept so I made a lot of mistakes. # Week 9 Blog post Analyzing Quadratic Functions of the Form Y=a$latex x^2\$+bx+c

Factored Form: y=a(x-x1)(x-x2)

y=-2 $x^2$ -6x+20

y=-2( $x^2$+3x-10)

y=-2(x1+5)(x2-2)

x1=-5  x2=2(x-intercepts)

so the axis of symmetry is (-5+2) devided by 2 equals to -1.5