Non-Right-Angled Triangle

Pythagorean Theorem

Find Unknown Side of a Right-Angled Triangle

Enter two known sides. Leave the unknown side blank. The theorem states $a^2 + b^2 = c^2$, where $c$ is the hypotenuse.

a b c (hyp)

Trigonometric Ratios (SOH CAH TOA)

For an acute angle $\theta$ in a right-angled triangle:

  • Sine ($\sin \theta$): $\frac{\text{Opposite}}{\text{Hypotenuse}}$ (SOH)
  • Cosine ($\cos \theta$): $\frac{\text{Adjacent}}{\text{Hypotenuse}}$ (CAH)
  • Tangent ($\tan \theta$): $\frac{\text{Opposite}}{\text{Adjacent}}$ (TOA)
Opposite (b) Adjacent (a) Hypotenuse (c) θ

Evaluate $\sin, \cos, \tan$

Reciprocal Trigonometric Ratios

  • Cosecant ($\csc \theta$): $\frac{1}{\sin \theta} = \frac{\text{Hypotenuse}}{\text{Opposite}}$
  • Secant ($\sec \theta$): $\frac{1}{\cos \theta} = \frac{\text{Hypotenuse}}{\text{Adjacent}}$
  • Cotangent ($\cot \theta$): $\frac{1}{\tan \theta} = \frac{\text{Adjacent}}{\text{Opposite}}$

Evaluate $\csc, \sec, \cot$

Common Angle Ratios (Exact Values)

Angle ($\theta$)$\sin \theta$$\cos \theta$$\tan \theta$
$0^\circ (0 \text{ rad})$$0$$1$$0$
$30^\circ (\pi/6 \text{ rad})$$\frac{1}{2}$$\frac{\sqrt{3}}{2}$$\frac{1}{\sqrt{3}}$ or $\frac{\sqrt{3}}{3}$
$45^\circ (\pi/4 \text{ rad})$$\frac{1}{\sqrt{2}}$ or $\frac{\sqrt{2}}{2}$$\frac{1}{\sqrt{2}}$ or $\frac{\sqrt{2}}{2}$$1$
$60^\circ (\pi/3 \text{ rad})$$\frac{\sqrt{3}}{2}$$\frac{1}{2}$$\sqrt{3}$
$90^\circ (\pi/2 \text{ rad})$$1$$0$Undefined

Solve Right-Angled Triangle

Find Unknown Sides and Angles

Provide exactly two pieces of information, including at least one positive side length. Angle C is assumed to be $90^\circ$.

Angles of Elevation and Depression

Angle of Elevation: The angle measured upwards from the horizontal line of sight to an object above the observer.

Observer Object θ (Elevation)

Angle of Depression: The angle measured downwards from the horizontal line of sight to an object below the observer.

Observer Object φ (Depression)

Elevation/Depression Problem Solver

Given the height of an object and the angle of elevation to its top from the ground, find the horizontal distance.

Trigonometric Approximations for Small Angles

For small angles $\theta$ (measured in radians):

  • $\sin \theta \approx \theta$
  • $\cos \theta \approx 1 - \frac{\theta^2}{2}$
  • $\tan \theta \approx \theta$

These approximations are useful in physics and engineering for simplifying complex equations under certain conditions.

Compare Exact vs. Approximation