These math apps for high school relate to the 8 Standards of Mathematical Practices as now required.
Google Chrome app: https://chrome.google.com/webstore/detail/bhdheahnajobgndecdbggfmcojekgdko
Website: https://www.desmos.com/
Edmodo app: http://www.edmodo.com/publisher?uid=3382251
Free iPad app: https://itunes.apple.com/us/app/graphing-calculator-by-desmos/id653517540?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/graphing-calculator-by-desmos/id653517540?mt=8&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.desmos.calculator
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.desmos.calculator
Website: http://fluidmath.net/
Free iPad app: https://itunes.apple.com/us/app/sketchpad-explorer/id452811793?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/geometry-pad/id517461177?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/algebra-genie/id481026577?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/algebra-genie/id481026577?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=air.com.zegenie.algebra
Paid iPad app: https://itunes.apple.com/app/ti-nspire/id590823242?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/algebra-touch/id384354262?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/algebra-touch/id384354262?mt=8&uo=4&at=10l6SU
Website: http://www.khanacademy.org/
Free iPad app: https://itunes.apple.com/us/app/id469863705?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/id469863705?mt=8&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=org.khanacademy.android
Free Android Tablet app: https://play.google.com/store/apps/details?id=org.khanacademy.android
Edmodo app: https://spotlight.edmodo.com/product/khan-academy,324527/
Paid Android Phone app: https://play.google.com/store/apps/details?id=com.wewanttoknow.DragonBoxPlus
Paid iPad app: https://itunes.apple.com/us/app/dragonbox-algebra-5+/id522069155?mt=8&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/dragonbox-algebra-5+/id522069155?mt=8&at=10l6SU
Paid Mac program: https://itunes.apple.com/us/app/dragonbox-algebra-5+/id524967552?mt=12&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/math-ref-free/id312756358?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/math-ref-free/id312756358?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/math-ref/id301384057?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/math-ref/id301384057?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/probability-tools/id544340525?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.visionobjects.calculator
Free iPhone app: https://itunes.apple.com/en/app/myscript-calculator/id578979413?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/en/app/myscript-calculator/id578979413?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/5-dice-order-operations-game/id572774867?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/5-dice-order-operations-game/id572774867?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/magicplan-csi/id480247904?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/magicplan-csi/id480247904?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/graphbook/id348741481?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/graphbook/id348741481?mt=8&uo=4&at=10l6SU
For Geometry in a 21st Century classroom, I think you must use map tools like Google Earth. Finding the best location to put a mall, trama center, main office, in a central location using incenter, circumcenter, and other geometric concepts using maps brings real application to the classroom.
Free iPad app: https://itunes.apple.com/us/app/google-earth/id293622097?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/google-earth/id293622097?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.google.earth
Free Mac program: http://www.google.com/earth/download/
Free Windows program: http://www.google.com/earth/download/
Google Chrome app: http://www.google.com/earth/explore/products/plugin.html
Mozilla Firefox extension: http://www.google.com/earth/explore/products/plugin.html
Apple Safari extension: http://www.google.com/earth/explore/products/plugin.html
Free iPad app: https://itunes.apple.com/us/app/geometriq-geometry-picture/id551984696?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/geometriq-geometry-picture/id551984696?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/math-with-your-friends-game/id1159371308?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/math-with-your-friends-game/id1159371308?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.mathwithyourfriends
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.mathwithyourfriends
Free iPad app: https://itunes.apple.com/us/app/mathspace/id586612052?mt=8&uo=4&at=10l6SU
Website: https://mathspace.com.au/
Paid iPad app: https://itunes.apple.com/us/app/3d-geometry/id555596048?mt=8&uo=4&at=10l6SU
Paid Mac program: https://itunes.apple.com/us/app/3d-geometry/id558182993?mt=12&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/numbler-free/id617010732?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/numbler-math-game/id569515022?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/numbler-free/id617010732?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/numbler-math-game/id569515022?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/gochart/id660032302?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/gochart/id660032302?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/ezymaths/id563471869?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/ezymaths/id563471869?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/ezy-graph/id627870001?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/ezy-graph/id627870001?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/ezy-triangle/id636410952?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/ezy-triangle/id636410952?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/ezy-trigonometry/id654848143?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/ezy-trigonometry/id654848143?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/dataanalysis/id375603883?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/isosceles-geometry-sketchpad/id554492532?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/isosceles-geometry-sketchpad/id554492532?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/isosceles+-geometry-sketchpad/id547654254?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/isosceles+-geometry-sketchpad/id547654254?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/wiled-math/id595171138?mt=8&uo=4&at=10l6SU
Free Mac program: http://www.geogebra.org/cms/download
Free Windows program: http://www.geogebra.org/cms/download
Google Chrome app: https://chrome.google.com/webstore/detail/geogebra/bnbaboaihhkjoaolfnfoablhllahjnee
Free iPad app: https://itunes.apple.com/us/app/myscript-mathpad-handwriting/id674996719?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/myscript-mathpad-handwriting/id674996719?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/dragonbox-algebra-12+-award/id634444186?mt=8&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/dragonbox-algebra-12+-award/id634444186?mt=8&at=10l6SU
Paid Mac program: https://itunes.apple.com/us/app/dragonbox-algebra-12+-award/id813681744?mt=12&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/gizmos/id692838319?mt=8&uo=4&at=10l6SU