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MathematicsClass 11CBSE
Find sin 75° Exactly, Without a Calculator, by Splitting It Into 45° and 30°
Expand sin and cos of sums and differences, use the tan and cot compound-angle formulae, convert between sums and products, and apply the double and triple angle identities for sine, cosine and tangent.
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Why the Sine of 150° Is Exactly the Same as the Sine of 30°
Define all six trigonometric functions with the unit circle, prove and use sin² x + cos² x = 1, find the sign of each function in every quadrant, evaluate allied angles, and state domains, ranges and periods with their graphs.
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Why Mathematicians Prefer Radians to Degrees for Measuring Angles
Represent positive and negative angles in standard position, convert between degree and radian measure with pi radians equal to 180 degrees, and use theta = l/r to find arc lengths, radii and angles at the centre.
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Why a Vending Machine Behaves Like a Function but a Lucky Dip Does Not
Decide whether a relation is a function, learn the domain, range and graph of the identity, constant, polynomial, rational, modulus, signum and greatest-integer functions, find domains and ranges from formulas, and combine real functions.
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Every Seat in a Cinema Hall Is an Ordered Pair of Row and Number
Form Cartesian products and count their elements, find unknowns from equal ordered pairs, write relations in roster, arrow-diagram and set-builder form, and find the domain, co-domain and range of a relation and the number of relations.
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Why Neither Tea Nor Coffee Means the Same as Not Tea and Not Coffee
Choose a universal set and draw Venn diagrams, find unions, intersections and differences, identify disjoint sets, take complements and verify De Morgan's laws, and use the laws of set algebra to simplify and prove identities.
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A Set of Just 10 Elements Has More Than a Thousand Subsets
Write sets in roster and set-builder form, decide whether a collection is well defined, classify empty, finite and infinite sets, test equality, count subsets with 2^n, and describe subsets of real numbers as intervals.
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Why a Coin That Landed Heads Five Times Is Still Fifty-Fifty Next Time
Learn what random experiments, sample spaces and events are, calculate the probability of a simple event, use P(not A) = 1 - P(A) with impossible and sure events, and solve problems on cards, coloured balls and numbered tickets.
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Why the Middle Value Can Tell a Truer Story Than the Average
Find the median of raw data and the median class of grouped data, find the mode and modal class, work out quartiles and the inter-quartile range, and find a missing frequency or value from a given mean or median.
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Three Ways to Find the Same Average, and Why the Last One Saves the Most Time
Find the mean of raw data and of a frequency table, then find the mean of grouped data by the direct method, the short-cut method and the step-deviation method — and see why all three give the same answer.
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One Curved Graph Reveals the Middle Mark of Fifty Students
Draw histograms for grouped data, estimate the mode with the diagonal construction, build a cumulative frequency table and less-than ogive, and read the median, quartiles and counts above or below a value from the curve.
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How Far Away Is That Boat? Angles From a Lighthouse Tell You
Define and mark angles of elevation and depression, find heights and distances with one right triangle, solve two-triangle problems on towers, and work out river widths, distances between boats and the height of a pole on a building.
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How Two Equations With the Same Angle Can Be Squeezed Into One Without It
Prove identities with fractions by taking the LCM or rationalising, eliminate theta from a pair of equations, use complementary-angle relations, and read four-figure trigonometric tables in both directions.
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One Right Triangle Hides Three Identities That Hold for Every Angle
Simplify expressions with sin² A + cos² A = 1, use 1 + tan² A = sec² A and 1 + cot² A = cosec² A, prove identities by writing everything in sine and cosine, and evaluate expressions at the standard angles.
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How Many Small Laddoos Can You Make From One Giant Laddoo?
Find the surface area and volume of combined solids, use melting and recasting to find new dimensions or counts, work with hollow cylinders and spheres, and calculate how far water rises or falls when a solid is immersed.
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Why the Label on a Tin Can Unrolls Into a Perfect Rectangle
Find the curved surface area, total surface area and volume of cylinders, cones, spheres and hemispheres, use slant height correctly, and work out the cost of painting, plastering or covering a solid.
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Draw a Circle Through All Three Corners of Any Triangle With Just Compasses
Construct a pair of tangents from an external point, circumscribe a circle about a triangle with perpendicular bisectors, inscribe a circle with angle bisectors, and draw both circles on a regular hexagon, checking every radius by calculation.
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Two Crossing Chords Always Cut Each Other Into Equal Products
Use the intersecting chords theorem for chords meeting inside and outside a circle, find tangent lengths with PT² = PA × PB, and solve incircle and circumcircle problems using equal tangents.
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A Bicycle Wheel Touches the Road at One Point, and That Point Is Special
Use the fact that a tangent is perpendicular to the radius, find lengths with equal tangents from an external point, handle circles that touch each other, and apply the alternate segment theorem to angles between a tangent and a chord.
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Why the Opposite Corners of a Quadrilateral in a Circle Always Add to 180°
Use the fact that opposite angles of a cyclic quadrilateral are supplementary, apply the exterior angle property, prove that four points are concyclic, and solve riders that mix cyclic properties with parallel lines and equal chords.
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Why Every Angle Drawn in a Semicircle Is Exactly a Right Angle
Use the theorem that the angle at the centre is double the angle at the circumference, find equal angles in the same segment, apply the right angle in a semicircle, and solve mixed problems with isosceles triangles and angle sums.
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Where Should a Water Tank Stand to Be Equally Far From Two Villages?
Learn what a locus is and describe loci in words, use the three standard loci, construct a perpendicular bisector and an angle bisector with ruler and compasses, and mark the points that satisfy two conditions at once.
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Double the Sides of a Triangle and Its Area Becomes Four Times as Big
Use the theorem on areas of similar triangles, find area ratios from medians, altitudes and perimeters, convert lengths, areas and volumes with map and model scales, and solve enlargement and reduction problems with a scale factor.
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How a Shadow Lets You Measure a Tree Without Ever Climbing It
Learn the SSS, SAS and AA conditions for similar triangles, tell similarity from congruency, use the Basic Proportionality Theorem and its converse, and find unknown sides from the ratio of corresponding sides.
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