Question

Show \(\cos \left(\frac{\pi}{2}-\theta\right)=\sin \theta\).

Short answer

Question: Show that \(\cos \left(\frac{\pi}{2}-\theta\right) = \sin \theta\). Answer: Using the angle subtraction formula, substituting the values of α and β, and simplifying using trigonometric identities, we find that \(\cos \left(\frac{\pi}{2}-\theta\right)=\sin\theta\).

Step-by-step solution

Recall the cosinus angle subtraction formula

The cos (angle subtraction) formula is given by: \(\cos(\alpha - \beta) = \cos\alpha\cos\beta + \sin\alpha\sin\beta\)

Substitute the values of α and β

Now, substitute the values \(\alpha = \frac{\pi}{2}\) and \(\beta = \theta\) in the cos (angle subtraction) formula: \(\cos \left(\frac{\pi}{2}-\theta\right) = \cos\left(\frac{\pi}{2}\right)\cos\theta + \sin\left(\frac{\pi}{2}\right)\sin\theta\)

Simplify the expression using trigonometric identities

We know that \(\cos\left(\frac{\pi}{2}\right)=0\) and \(\sin\left(\frac{\pi}{2}\right)=1\), so by substituting these values into the formula, we have: \(\cos \left(\frac{\pi}{2}-\theta\right) = 0 \cdot \cos\theta + 1 \cdot \sin\theta\) Thus, \(\cos \left(\frac{\pi}{2}-\theta\right)=\sin\theta\), as we needed to show.

Key concepts

Cosine Angle Subtraction Formula

The cosine angle subtraction formula is a fundamental affair in trigonometry, a branch of mathematics teeming with applications in both pure and applied subjects, including engineering.

The formula itself is written as: \[\begin{equation}\cos(\alpha - \beta) = \cos\alpha\cos\beta + \sin\alpha\sin\beta\end{equation}\] This tidy expression allows us to find the cosine of the difference between any two angles, a capability that's indispensable in fields such as physics, computer graphics, and signal processing.

When you encounter an exercise involving the cosine of an angle subtraction, such as \(\cos (\frac{\pi}{2}-\theta)\), reach for this powerful formula. You'll substitute the given angle values into \(\alpha\) and \(\beta\) and then apply known trigonometric identities to simplify the expression—like knowing the sine and cosine values of \(\frac{\pi}{2}\). It's like having a mathematical Swiss Army knife at your disposal!

Trigonometric Functions

At the heart of trigonometry, trigonometric functions map angles to corresponding ratios of sides in right-angled triangles.

There's a veritable star cast of six functions, but the leads are sine (\(\sin\)), cosine (\(\cos\)), and tangent (\(\tan\)). Each function has a different character; \(\sin\) relates the opposite side to the hypotenuse, while \(\cos\) relates the adjacent side to the hypotenuse.

Imagine you're an engineer analyzing the stability of a bridge. You use trigonometric functions to calculate forces and angles ensuring it can withstand high winds, because these functions describe how waveforms behave—in the physical world and in calculations.

Remember their unit circle values, like \(\sin(\frac{\pi}{2}) = 1\) and \(\cos(\frac{\pi}{2}) = 0\), to solve equations swiftly! Trigonometric functions are the versatile language in which we write the geometry of the universe.

Mathematics for Engineers

For engineers, mathematics is a trusted tool, as essential as a hard hat on a construction site. Trigonometry, calculus, and algebra are just the tip of the engineering mathematics iceberg.

Mathematics is employed by engineers to design, analyze, and improve upon the myriad structures and systems that make our world work—from the software in our phones to the bridges spanning our rivers.

In the context of trigonometry, grasping concepts like the cosine angle subtraction formula enables engineers to predict system behaviors, optimize designs, and solve complex problems where angles and distances are crucial. Learning to prove identities as in the exercise \(\cos (\frac{\pi}{2}-\theta)=\sin \theta\) not only sharpens problem-solving skills but also lays down the groundwork for advanced understanding—vital for any engineer worth their salt.