 Home > Trigonometry The identify $\cos^2 \theta + \sin^2 \theta = 1$ is required for finding trigonometric ratios. Example 1 Find exactly the possible values of $\cos \theta$ for $\sin \theta = \dfrac{5}{8}$. Show Solution \begin{align} \displaystyle \cos^2 \theta + \sin^2 \theta &= 1 \\ \cos^2 \theta + \sin^2 \dfrac{5}{8} &= 1 \\ \cos^2 [...] # Trigonometric Ratios Home > Trigonometry Circles with Cnetre (0,0) Consider a circle with centre (0,0) and radius r units. Suppose (x,y) is any point on this circle. Using ths distance formula; \( \begin{align} \displaystyle \sqrt{(x-0)^2+(y-0)^2} &= r \\ \therefore x^2+y^2 &= r^2 \end{align} $x^2+y^2 = r^2$ is the equation of a circle with centre $(0,0)$ and [...] Home > Trigonometry Degree Measurement of Angles One full revolution makes an angle of $360^{\circ}$, and the angle on a straight line is $180^{\circ}$. Therefore, one degree, $1^{\circ}$, can be defined as $\dfrac{1}{360}$ of one full revolution. For greater accuracy we define one minute, $1'$, as $\dfrac{1}{60}$ of one degree and one second, $1''$, as [...] Share0 Share +10 Tweet0 One of the most effective ways to solve Three Dimensional Trigonometry questions is to list all of the trigonometric ratios appeared in the questions. Then connect each relevant ratios to the question. Worked Examples of Three Dimensional Trigonometry Question 1 $X$ and $Y$ are two points on the same bank of […] 