Here is a link to the playlist of video explanations to all of the math questions in the 2020 December ACT (Form D03) Test.
Right triangles and trigonometric expressions: ACT Math Practice Question
Try the following ACT math practice question that tests your understanding of evaluating trigonometric expressions in the context of right triangles.
In the right triangle $ABC$ shown below, what is the value of $1 – \cos^2{A} – \cos^2{B}$ ?
 $\quad 1$
 $\quad \displaystyle \frac{1}{2}$
 $\quad \displaystyle \hskip 0.8em 0$
 $\quad \displaystyle \hskip 0.8em 1$
 $\quad \displaystyle \hskip 0.6em \frac{1}{2}$
Review of The Official Beginner’s Guide for ACT 20202021
Here is a quick summary of what is new about The Official Beginner’s Guide for ACT 20202021 1st Edition that was released in February 2020.

PreACT Diagnostic Test: The guide provides online access to one full length PreACT diagnostic test that can be used by 9th to 12th graders(highly recommended for 10th graders) to predict student performance on the ACT test. This PreACT diagnostic test was originally administered as PreACT Form 16A in October of 2016.

ACT Practice Test (Form 20MC7): The guide contains one full length ACT practice test and this test is identical to the 2018 April ACT Test Form A09. The book also provides access to this same test in an online format.
My recommendation is to not buy this guide, and instead practice with the two original official tests that are included in this guide: PreACT Form 16A and 2018 April ACT Test Form A09.
Circles and intersections with xaxis: ACT Math Practice Question
Try this ACT math practice question that tests your ability to find the xintercepts of circles.
The circle $(x+1)^2+(y2)^2=29$ intersects the $x$axis in two points, one of which is $(4,0)$. What are the coordinates of the other point where the circle intersects the $x$axis?
 $\quad (7, 0)$
 $\quad (6, 0)$
 $\quad (\sqrt{29}, 0)$
 $\quad (5, 0)$
 $\quad (4, 0)$
Simplifying a hard trigonometric expression: ACT Math Practice Question
Try this ACT math practice question that tests your ability to algebraically simplify a trigonometric expression using trigonometric identities.
$$\dfrac{\cos \theta}{1 – \sin \theta} \quad – \quad \dfrac{\sin \theta}{\cos \theta}$$
When $\cos \theta \neq 0$ and $\sin \theta \neq 1$, which of the following is equivalent to the expression above?
 $\quad \sec \theta$
 $\quad \csc \theta$
 $\quad \cos \theta$
 $\quad \cos^{2} \theta$
 $\quad \dfrac{\cos \theta – \sin \theta}{(\cos \theta)(1 – \sin \theta)}$
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