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ACT · Math · Preparing for Higher Math: Geometry
Right triangles and trigonometry is part of Preparing for Higher Math: Geometry in the ACT Math section. The questions below are written in the style of the real test, each with the answer and a worked explanation.
Question types you will see here include find a side with a trig ratio, trig ratio from side lengths, pythagorean theorem and special right triangles.
Common traps: choosing sine when tangent is needed; multiplying when division is needed; calculator set to the wrong angle mode.
Question 1
In right triangle ABC, angle C is the right angle, BC = 3, AC = 4, and AB = 5. What is the value of sin(A)?
3/5
3/4
4/5
5/3
Answer: A. 3/5
For angle A, side BC is opposite and AC is adjacent. sin(A) = opposite/hypotenuse = BC/AB = 3/5.
A few questions show the style. The free scan shows which ACT skills cost you the most points, then builds a plan around them.