Problem preview
F-TF.8 Warmup M2-028-A07-V01

Prove and use sin^2(theta)+cos^2(theta)=1 to find trig values with quadrant information.

Find a missing unit-circle coordinate using the Pythagorean identity and quadrant information

Problem

A point on the unit circle is \((3/5,~y)\) in \(\text{Quadrant}~I\). Find the missing coordinate.

Big Picture

What this problem is really about

A point lies on the unit circle only when its squared coordinates add to one, which determines a missing coordinate’s magnitude. We’ll substitute the known coordinate, take both square roots, use the quadrant to set the sign, and verify the completed point in the circle equation.

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Four variants of this problem type
Curriculum context
Course
Math II
Standard
F-TF.8
Category
Functions
Domain
Trigonometric Functions
Objective
Prove and use sin^2(theta)+cos^2(theta)=1 to find trig values with quadrant information.
Problem type
Find a missing unit-circle coordinate using the Pythagorean identity and quadrant information